125876 + Interview Questions in General QA

1.	Translate the following statements into chemical equations and then balance the equations :(a) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.(b) Phosphorus burns in oxygen to give phosphorus pentoxide.(c) Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.(d) Aluminium metal replaces iron from ferric oxide, Fe O , giving aluminium oxide and iron.(e) Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.
Answer» (a) 2H₂S + 3O₂ —–> 2H₂O + 2SO₂ (b) P₄ + 5O₂ —–> 2P₂O₅ (c) CS₂ + 3O₂ —–> CO₂ + 2SO₂ (d) 2Al + Fe₂O₃ —–> Al₂O₃ + 2Fe (e) BaCl₂ + ZnCO₄ —–> ZnCl₂ + BaSO₄

1.

Translate the following statements into chemical equations and then balance the equations :(a) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.(b) Phosphorus burns in oxygen to give phosphorus pentoxide.(c) Carbon disulphide burns in air to give carbon dioxide and sulphur dioxide.(d) Aluminium metal replaces iron from ferric oxide, Fe O , giving aluminium oxide and iron.(e) Barium chloride reacts with zinc sulphate to give zinc chloride and barium sulphate.

Answer»

(a) 2H₂S + 3O₂ —–> 2H₂O + 2SO₂

(b) P₄ + 5O₂ —–> 2P₂O₅

(c) CS₂ + 3O₂ —–> CO₂ + 2SO₂

(d) 2Al + Fe₂O₃ —–> Al₂O₃ + 2Fe

(e) BaCl₂ + ZnCO₄ —–> ZnCl₂ + BaSO₄

Discussion

2.	Write the balanced chemical equations for the following reactions :(a) Calcium hydroxide + Carbon dioxide ——> Calcium carbonate + Water(b) Aluminium + Copper chloride ——– > Aluminium chloride + Copper
Answer» (a) Ca(OH)₂ + CO₂ —–> CaCO₃ + H₂O2Al + 3CuCl₂ —–> 2AlCl₃ + 3Cu

Discussion

3.	Write a balanced chemical equation with state symbols for Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.
Answer» NaOH(aq) + HCl(aq) ➝ NaCl(aq)+ H₂O(l)

Discussion

4.	A solution of a substance ‘X’ is used for whitewashing. Name the substance ‘X’ and write its formula.
Answer» The substance X is calcium Hydroxide. Its formula is Ca(OH)₂

Discussion

5.	Coal and petroleum have been formed from biomass which has been subjected to various biological and geological processes. Coal is the remains of trees, ferns, and other plants that lived millions of years ago. These were crushed into the earth, perhaps by earthquakes or volcanic eruptions. They were pressed down by layers of earth and rock. They slowly decayed into coal. Oil and gas are the remains of millions of tiny plants and animals that lived in the sea. When they died, their bodies sank to the sea bed and were covered by silt. Bacteria attacked the dead remains, turning them into oil and gas under the high pressures they were being subjected to. Meanwhile, the silt was slowly compressed into rock. The oil and gas seeped into the porous parts of the rock, and got trapped like water in a sponge.1. _____ is the remains of trees, ferns and all other plants that lived millions of years ago.(i) Smoke(ii) Coal(iii) Plastic(iv) None of these2. State true or false: Oil and gas are the remains of millions of big plants and animals that lived in the sea.(i) TRUE(ii) FALSE3. True or false. Coal and petroleum are called fossil fuels.(i) TRUE(ii) FALSE4. The remains of trees, ferns, and other plants that lived millions of years ago slowly decayed into______.(i) Smoke(ii) Coal(iii) Plastic(iv) None of these5. True or false. The oil and gas seeped into the porous parts of the rock, and got trapped like air in a sponge.(i) TRUE(ii) FALSE
Answer» 1. (ii) Coal 2. (i) TRUE 3. (i) TRUE 4. (ii) Coal 5. (ii) FALSE

5.

Coal and petroleum have been formed from biomass which has been subjected to various biological and geological processes. Coal is the remains of trees, ferns, and other plants that lived millions of years ago. These were crushed into the earth, perhaps by earthquakes or volcanic eruptions. They were pressed down by layers of earth and rock. They slowly decayed into coal. Oil and gas are the remains of millions of tiny plants and animals that lived in the sea. When they died, their bodies sank to the sea bed and were covered by silt. Bacteria attacked the dead remains, turning them into oil and gas under the high pressures they were being subjected to. Meanwhile, the silt was slowly compressed into rock. The oil and gas seeped into the porous parts of the rock, and got trapped like water in a sponge.1. _ is the remains of trees, ferns and all other plants that lived millions of years ago.(i) Smoke(ii) Coal(iii) Plastic(iv) None of these2. State true or false: Oil and gas are the remains of millions of big plants and animals that lived in the sea.(i) TRUE(ii) FALSE3. True or false. Coal and petroleum are called fossil fuels.(i) TRUE(ii) FALSE4. The remains of trees, ferns, and other plants that lived millions of years ago slowly decayed into__.(i) Smoke(ii) Coal(iii) Plastic(iv) None of these5. True or false. The oil and gas seeped into the porous parts of the rock, and got trapped like air in a sponge.(i) TRUE(ii) FALSE

Answer»

1. (ii) Coal

2. (i) TRUE

3. (i) TRUE

4. (ii) Coal

5. (ii) FALSE

Discussion

6.	A solution of a substance ‘X’ is used for whitewashing(i) Name the substance ‘X’ and write its formula.(ii) Write the reaction of the substance ‘X’ named in (i) above with water.
Answer» (i) The substance ‘X’ which is used in whitewashing is quick lime or Calcium Oxide and its formula is CaO. (ii) CaO + H₂O → Ca(OH)₂

6.

A solution of a substance ‘X’ is used for whitewashing(i) Name the substance ‘X’ and write its formula.(ii) Write the reaction of the substance ‘X’ named in (i) above with water.

Answer»

(i) The substance ‘X’ which is used in whitewashing is quick lime or Calcium Oxide and its formula is CaO.

(ii) CaO + H₂O → Ca(OH)₂

Discussion

7.	(a) Potassium chlorate (KClO3) on heating forms potassium chloride and oxygen. Write a balanced equation for this reaction and indicate the evolution of gas. (b) Rewrite the following information in the form of a balanced chemical equation : Magnesium burns in carbon dioxide to form magnesium oxide and carbon.
Answer» (a) 2KClO₃ (s) 2KCl (s) + 3O₂ (g) (b) 2Mg + CO₂ —–> 2MgO + C

7.

(a) Potassium chlorate (KClO3) on heating forms potassium chloride and oxygen. Write a balanced equation for this reaction and indicate the evolution of gas. (b) Rewrite the following information in the form of a balanced chemical equation : Magnesium burns in carbon dioxide to form magnesium oxide and carbon.

Answer»

(a) 2KClO₃

(s) 2KCl (s) + 3O₂ (g)

(b) 2Mg + CO₂ —–> 2MgO + C

Discussion

8.	If the valencies of all the atoms are satis4ed by single bonds between them, then such carbon compounds are called saturated compounds. These compounds are normally not very reactive. However, another compound of carbon and hydrogen has the formula \(C_2H_4\) and is called ethene. One valency per carbon atom remains unsatisfied in ethene. This can be satisfied only if there is a double bond between the two carbons.1. Saturated compounds have ____kind of bond.(i) Single(ii) Double(iii) Triple(iv) None of these2. Ethene has_____bond.(i) Single(ii) Double(iii) Triple(iv) None of these3. The valency of carbon atom in ethene is only satisfied if there is a bond between them. True or false?(i) TRUE(ii) FALSE4. Are saturated compounds reactive?(i) YES(ii) NO5. Are Alkynes compounds reactive?(i) YES(ii) NO
Answer» 1. (i) Single 2. (ii) Double 3. (i) (i) TRUE 4. (ii) NO 5. (i) YES

8.

If the valencies of all the atoms are satis4ed by single bonds between them, then such carbon compounds are called saturated compounds. These compounds are normally not very reactive. However, another compound of carbon and hydrogen has the formula \(C_2H_4\) and is called ethene. One valency per carbon atom remains unsatisfied in ethene. This can be satisfied only if there is a double bond between the two carbons.1. Saturated compounds have kind of bond.(i) Single(ii) Double(iii) Triple(iv) None of these2. Ethene has_bond.(i) Single(ii) Double(iii) Triple(iv) None of these3. The valency of carbon atom in ethene is only satisfied if there is a bond between them. True or false?(i) TRUE(ii) FALSE4. Are saturated compounds reactive?(i) YES(ii) NO5. Are Alkynes compounds reactive?(i) YES(ii) NO

Answer»

1. (i) Single

2. (ii) Double

3. (i) (i) TRUE

4. (ii) NO

5. (i) YES

Discussion

9.	Translate into chemical equations and then balance Hydrogen gas combines with nitrogen to form ammonia.
Answer» 3H₂(g) + N₂(g) ➝ 2NH₃(g)

Discussion

10.	Chemical reaction in which a more reactive element displaces a less reactive element from its compound is called as displacement reaction. Both metals and non-metals take part in displacement reactions. Some applications of displacement reactions are thermite welding, steel making, extraction of metals, and relief from acid indigestion.1. What is the type of the chemical reaction: AgNO3 + HCl \(\longrightarrow\) Agcl + HNO3(i) Double displacement reaction(ii) Single displacement reaction(iii) Decomposition reaction(iv) Combination reaction2. What is the type of the chemical reaction: Mg + 2HCl \(\longrightarrow\) MgCl2 + 2H2(i) Double displacement reaction(ii) Single displacement reaction(iii) Decomposition reaction(iv) Combination reaction3. What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?(i) Iron nails become brownish in colour(ii) Blue colour of copper sulphate solution fades(iii) Both (1) and (2)(iv) No change4. In the above image, What are the reducing and oxidising agent?(i) H2S is reducing agent and SO2 is oxidising agent(ii) H2S is oxidising agent and SO2 is reducing agent(iii) H2O is oxidising agent and SO2 is reducing agent(iv) S is oxidising agent and SO2 is reducing agent5. State true or false: Butylated hydroxyanisole (BHA) is synthetic antioxidant(i) TRUE(ii) FALSE
Answer» 1. (i) Double displacement reaction 2. (ii) Single displacement reaction 3. (iii) Both (i) and (ii) 4. (i) H₂S is reducing agent and SO₂ is oxidising agent 5. (i) TRUE

10.

Chemical reaction in which a more reactive element displaces a less reactive element from its compound is called as displacement reaction. Both metals and non-metals take part in displacement reactions. Some applications of displacement reactions are thermite welding, steel making, extraction of metals, and relief from acid indigestion.1. What is the type of the chemical reaction: AgNO3 + HCl \(\longrightarrow\) Agcl + HNO3(i) Double displacement reaction(ii) Single displacement reaction(iii) Decomposition reaction(iv) Combination reaction2. What is the type of the chemical reaction: Mg + 2HCl \(\longrightarrow\) MgCl2 + 2H2(i) Double displacement reaction(ii) Single displacement reaction(iii) Decomposition reaction(iv) Combination reaction3. What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails dipped in copper sulphate solution for about 30 minutes?(i) Iron nails become brownish in colour(ii) Blue colour of copper sulphate solution fades(iii) Both (1) and (2)(iv) No change4. In the above image, What are the reducing and oxidising agent?(i) H2S is reducing agent and SO2 is oxidising agent(ii) H2S is oxidising agent and SO2 is reducing agent(iii) H2O is oxidising agent and SO2 is reducing agent(iv) S is oxidising agent and SO2 is reducing agent5. State true or false: Butylated hydroxyanisole (BHA) is synthetic antioxidant(i) TRUE(ii) FALSE

Answer»

1. (i) Double displacement reaction

2. (ii) Single displacement reaction

3. (iii) Both (i) and (ii)

4. (i) H₂S is reducing agent and SO₂ is oxidising agent

5. (i) TRUE

Discussion

11.	What is a balanced chemical equation ? Why should chemical equation be balanced ?
Answer» The equation in which atoms of various elements on both sides of a chemical equation are equal in accordance with the law of conservation of mass is known as balanced chemical equation. The chemical equation is to be balanced in accordance to the law of conservation of mass. It means the total mass of the elements present in the products of a chemical reaction has to be equal to the total mass of the elements present in the reactants. In other words, the number of atoms of each element remains the same, before and after a chemical react'ion. Hence, we need to balance a chemical equation

11.

What is a balanced chemical equation ? Why should chemical equation be balanced ?

Answer»

The equation in which atoms of various elements on both sides of a chemical equation are equal in accordance with the law of conservation of mass is known as balanced chemical equation.

The chemical equation is to be balanced in accordance to the law of conservation of mass. It means the total mass of the elements present in the products of a chemical reaction has to be equal to the total mass of the elements present in the reactants. In other words, the number of atoms of each element remains the same, before and after a chemical react'ion. Hence, we need to balance a chemical equation

Discussion

12.	Gas A, which is the major cause of global warming, combines with hydrogen oxide B in nature in the presence of an environmental factor C and a green material D to form a six carbon organic compound E and a gas F. The gas F is necessary for breathing.(a) What is gas A ?(b) What is the common name of B ?(c) What do you think could be C ?(d) What is material D ? Where is it found ?
Answer» (a) Carbon dioxide,CO₂ (b) Water, H₂O (c) Sunlight. (d) Chlorophyll;Green leaves of plants. (e) Glucose, C₆H₁₂O₆ (f) Oxygen; Photosynthesis.

12.

Gas A, which is the major cause of global warming, combines with hydrogen oxide B in nature in the presence of an environmental factor C and a green material D to form a six carbon organic compound E and a gas F. The gas F is necessary for breathing.(a) What is gas A ?(b) What is the common name of B ?(c) What do you think could be C ?(d) What is material D ? Where is it found ?

Answer»

(a) Carbon dioxide,CO₂

(b) Water, H₂O

(c) Sunlight.

(d) Chlorophyll;Green leaves of plants.

(e) Glucose, C₆H₁₂O₆

(f) Oxygen;

Photosynthesis.

Discussion

13.	Whenever a chemical change occurs, we can say that a chemical reaction has taken place. A schematic representation of any chemical reaction with the help of symbols and formulas of various species is called a chemical equation. A chemical equation should include all the information regarding the reaction.1. The gaseous state of reactants and products is represented by which of the following symbol?(i) (g)(ii) (gas)(iii) (ga)(iv) None of the above2. The solid state of reactants and products is represented by which of the following symbol?(i) (solid)(ii) (s)(iii) (sld)(iv) None of the above3. The liquid state of reactants and products is represented by which of the following symbol?(i) (l)(ii) (aqueous)(iii) (aq)(iv) None of the above4. State true or false: The word aqueous (aq) is written if the reactant or product is present in liquid state.(i) TRUE(ii) FALSE5. State true or false: The reaction conditions, such as temperature, pressure, catalyst, etc., for the reaction are indicated only above the arrow in the equation.(i) TRUE(ii) FALSE
Answer» 1. (i) (g) 2. (ii) (s) 3. (i) (l) 4. (ii) FALSE 5. (ii) FALSE

13.

Whenever a chemical change occurs, we can say that a chemical reaction has taken place. A schematic representation of any chemical reaction with the help of symbols and formulas of various species is called a chemical equation. A chemical equation should include all the information regarding the reaction.1. The gaseous state of reactants and products is represented by which of the following symbol?(i) (g)(ii) (gas)(iii) (ga)(iv) None of the above2. The solid state of reactants and products is represented by which of the following symbol?(i) (solid)(ii) (s)(iii) (sld)(iv) None of the above3. The liquid state of reactants and products is represented by which of the following symbol?(i) (l)(ii) (aqueous)(iii) (aq)(iv) None of the above4. State true or false: The word aqueous (aq) is written if the reactant or product is present in liquid state.(i) TRUE(ii) FALSE5. State true or false: The reaction conditions, such as temperature, pressure, catalyst, etc., for the reaction are indicated only above the arrow in the equation.(i) TRUE(ii) FALSE

Answer»

1. (i) (g)

2. (ii) (s)

3. (i) (l)

4. (ii) FALSE

5. (ii) FALSE

Discussion

14.	What type of reaction is represented by the digestion of food in our body ?
Answer» Decomposition reaction

Discussion

15.	When iron rod is kept dipped in copper sulphate solution for some time, a brown coating is formed on the iron rod. What change will be observed in the colour of the solution? Also write chemical equation for the reaction involved
Answer» Blue colour of the solution changes to light green. Reddish brown deposit is formed on the iron nail. Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)

15.

When iron rod is kept dipped in copper sulphate solution for some time, a brown coating is formed on the iron rod. What change will be observed in the colour of the solution? Also write chemical equation for the reaction involved

Answer»

Blue colour of the solution changes to light green. Reddish brown deposit is formed on the iron nail.

Fe(s) + CuSO₄(aq) → FeSO₄(aq) + Cu(s)

Discussion

16.	The main gate of ravi's house is developing a powdery brown film of substance which is slowly deteriorating the gate. He asked his friend ramu for help who told him to paint the gate in order to protect it from deteriorating.1. What is the chemical formula of the powdery brown film of the substance?(i) Fe2O3. xH2O(ii) FeO3. xH2O(iii) Fe2O3. xH2O(iv) None of the above2. Which of the following elements undergoes corrosion?(i) Gold(ii) Silver(iii) Platinum(iv) All of the above3. Which of the following is(are) the other ways in which the gate can be protected?(i) Applying the film of grease and oil on the metal surface(ii) Covering metal surface of metal with another metal which is more electropositive(iii) All of the above4. State true or false: Silver sulphide is the chemical name of the compound formed on corrosion of silver.(i) TRUE(ii) FALSE5. State true or false: Conversion of metals into their undesirable compounds (sulphides, carbonates, oxides, etc) by interaction with atmospheric gases and moisture is called as corrosion.(i) TRUE(ii) FALSE
Answer» 1. (i) Fe₂O₃xH₂O 2. (ii) Silver 3. (iii) All of the above 4. (i) TRUE 5. (i) TRUE

16.

The main gate of ravi's house is developing a powdery brown film of substance which is slowly deteriorating the gate. He asked his friend ramu for help who told him to paint the gate in order to protect it from deteriorating.1. What is the chemical formula of the powdery brown film of the substance?(i) Fe2O3. xH2O(ii) FeO3. xH2O(iii) Fe2O3. xH2O(iv) None of the above2. Which of the following elements undergoes corrosion?(i) Gold(ii) Silver(iii) Platinum(iv) All of the above3. Which of the following is(are) the other ways in which the gate can be protected?(i) Applying the film of grease and oil on the metal surface(ii) Covering metal surface of metal with another metal which is more electropositive(iii) All of the above4. State true or false: Silver sulphide is the chemical name of the compound formed on corrosion of silver.(i) TRUE(ii) FALSE5. State true or false: Conversion of metals into their undesirable compounds (sulphides, carbonates, oxides, etc) by interaction with atmospheric gases and moisture is called as corrosion.(i) TRUE(ii) FALSE

Answer»

1. (i) Fe₂O₃xH₂O

2. (ii) Silver

3. (iii) All of the above

4. (i) TRUE

5. (i) TRUE

Discussion

17.	A copper plate was dipped into a solution of silver nitrate. After sometime, a black layer was observed on the surface of copper plate. State the reason for it and write chemical equation of the reaction involved.
Answer» Black layer was deposited due to the coating of silver because copper being more reactive than silver, displaced silver from silver nitrate solution. 2AgNO₃(aq)+Cu → Cu(NO₃)₂(aq)+2Ag(S)

17.

A copper plate was dipped into a solution of silver nitrate. After sometime, a black layer was observed on the surface of copper plate. State the reason for it and write chemical equation of the reaction involved.

Answer»

Black layer was deposited due to the coating of silver because copper being more reactive than silver, displaced silver from silver nitrate solution.

2AgNO₃(aq)+Cu → Cu(NO₃)₂(aq)+2Ag(S)

Discussion

18.	Why is photosynthesis considered an endothermic reaction ?
Answer» Because heat is absorbed in this process.

Discussion

19.	Define endothermic reaction.
Answer» Endothermic reaction: Reaction in which heat is absorbed.

Discussion

20.	Why is photosynthesis considered as an endothermic reaction?
Answer» Photosynthesis is an endothermic reaction because it requires energy in the form of sunlight.

Discussion

21.	What is chemistry?
Answer» Chemistry: The study of the elements and the compounds they form.

Discussion

22.	State whether the following statement is true or false :A chemical equation can be balanced easily by altering the formula of a reactant or product.
Answer» The formula of a reactant or product. False.

22.

State whether the following statement is true or false :A chemical equation can be balanced easily by altering the formula of a reactant or product.

Answer»

The formula of a reactant or product.

False.

Discussion

23.	What is crystal?
Answer» Crystal: A solid in which atoms are arranged in a regular pattern.

Discussion

24.	What is wrong with the following chemical equation ?Mg + O ——— > MgOCorrect and balance it.
Answer» Oxygen should be in molecular form, O₂ 2Mg + O₂ —–> 2MgO

24.

What is wrong with the following chemical equation ?Mg + O ——— > MgOCorrect and balance it.

Answer»

Oxygen should be in molecular form, O₂

2Mg + O₂ —–> 2MgO

Discussion

25.	An oxidation reaction involves addition of …………………… A) oxygen only B) hydrogen only C) oxygen or removal of hydrogen D) hydrogen or removal of oxygen
Answer» C) oxygen or removal of hydrogen

Discussion

26.	Which is true about oxidation ? A) It involves loss of electrons. B) It involves addition of oxygen. C) It involves removal of hydrogen.D) All are true.
Answer» D) All are true.

Discussion

27.	Sheena was very excited to see her Aunt after a long time. Her mother fried a lot of snacks for her Aunt. Suddenly Sheena came to know that her aunt has postponed her plan for tomorrow. Sheena's mother got worried to know this. She thought the food will get spoiled Sheena helped her mother to preserve the food.Answer the following questions based on above passage.(i) Why does food spoil when kept for a very long time?(ii) What method did Sheena suggest her mother to preserve the food?(iii) What values are shown by Sheena?
Answer» (i) When food is kept for a very long time, it gets oxidized and becomes rancid. (ii) Sheena suggested her mother to keep the snacks in an air tight container. (iii) Intelligence, applying knowledge, helpful

Discussion

28.	Four friends went to a picnic. The weather was pleasant. They played various tames and then had snacks. Suddenly, Shyam one of them noticed seven colours in the sky. He said to others, "Wow what a rainbow"? The Ram, one of them, asked him "What is Rainbow"? He then explained to all about its formation. After that everyone in the group thanked him for the knowledge, he had given to them. (i) If you were in the place of Shyam, how you would have explained such a natural phenomenon.(ii) Which device can be used to obtain such a phenomenon. (iii) If Shyam was facing the rainbow, the where was the sun ?(iv) What is the moral value which is shown by Shyam?
Answer» (i) Rainbow is formed by the dispersion of Sunlight by the tiny water droplets present in the atmosphere after the rainfall. These water droplets act like a prism. Rays of Sunlight enter the water droplets. At the points of incidence, they refract and disperse, then gets reflected internally and finally gets refracted again at the point of emergence. Thus, the different colors of this spectrum called rainbow to reach the observer's eye. (ii) Prism. (iii) The Sun was behind Shyam. (iv) Knowledge increases by sharing, friendship, love and affection with nature.

28.

Four friends went to a picnic. The weather was pleasant. They played various tames and then had snacks. Suddenly, Shyam one of them noticed seven colours in the sky. He said to others, "Wow what a rainbow"? The Ram, one of them, asked him "What is Rainbow"? He then explained to all about its formation. After that everyone in the group thanked him for the knowledge, he had given to them. (i) If you were in the place of Shyam, how you would have explained such a natural phenomenon.(ii) Which device can be used to obtain such a phenomenon. (iii) If Shyam was facing the rainbow, the where was the sun ?(iv) What is the moral value which is shown by Shyam?

Answer»

(i) Rainbow is formed by the dispersion of Sunlight by the tiny water droplets present in the atmosphere after the rainfall. These water droplets act like a prism. Rays of Sunlight enter the water droplets. At the points of incidence, they refract and disperse, then gets reflected internally and finally gets refracted again at the point of emergence. Thus, the different colors of this spectrum called rainbow to reach the observer's eye.

(ii) Prism.

(iii) The Sun was behind Shyam.

(iv) Knowledge increases by sharing, friendship, love and affection with nature.

Discussion

29.	What does the symbol (aq) represent in a chemical equation ?
Answer» The symbol (aq) represents aqueous solution in a chemical equation.

29.

What does the symbol (aq) represent in a chemical equation ?

Answer»

The symbol (aq)

represents aqueous solution in a chemical equation.

Discussion

30.	How will you indicate the following effects in a chemical equation ?(a) A solution made in water(b) Exothermic reaction(c) Endothermic reaction
Answer» (a) Aqueous solution is indicated by the symbol ‘aq’. An exothermic reaction is indicated by writing “+Heat” or “+Heat energy” or “+Energy” on the products side of an equation. An endothermic reaction is indicated by writing “+Heat” or “+Heat energy” or “+Energy” on the reactants side of an equation.

30.

How will you indicate the following effects in a chemical equation ?(a) A solution made in water(b) Exothermic reaction(c) Endothermic reaction

Answer»

(a) Aqueous solution is indicated by the symbol ‘aq’.

An exothermic reaction is indicated by writing “+Heat” or “+Heat energy” or “+Energy” on the products side of an equation.

An endothermic reaction is indicated by writing “+Heat” or “+Heat energy” or “+Energy” on the reactants side of an equation.

Discussion

31.	Explain the corrosion with one example.
Answer» When a metal is attacked by substances around it such as moisture, acids etc., it is said to corrode and this process is called corrosion. Eq: The black coating on silver and the green coating on copper.

31.

Explain the corrosion with one example.

Answer»

When a metal is attacked by substances around it such as moisture, acids etc., it is said to corrode and this process is called corrosion.

Eq: The black coating on silver and the green coating on copper.

Discussion

32.	What is quicklime? Write one use of quicklime.
Answer» Calcium oxide is called lime or quicklime. It is used in the manufacture of cement.

Discussion

33.	Explain the rancidity with one example.
Answer» When fats and oils are oxidised, they become rancid and their smell and taste change. We can prevent Rancidity by following methods: 1. Preserving food material in air tight container. 2. We can preserve food items in Refrigerator. 3. By adding antioxidants. 4. By Flushing with Nitrogen to prevent oxidation.

33.

Explain the rancidity with one example.

Answer»

When fats and oils are oxidised, they become rancid and their smell and taste change.

We can prevent Rancidity by following methods:

1. Preserving food material in air tight container.

2. We can preserve food items in Refrigerator.

3. By adding antioxidants.

4. By Flushing with Nitrogen to prevent oxidation.

Discussion

34.	What is tarnish?
Answer» Tarnish: To make something lose its shine and make it dull because of oxidation or rust.

Discussion

35.	Give an example, each for thermal decomposition and photochemical decomposition reactions. Write balanced equation for the same.
Answer» Thermal Decomposition: Heating of lime stone CaCO₃ → CaO+CO₂ Photochemical Decomposition: Action of light on silver bromide. 2AgBr 2Ag + Br₂

35.

Give an example, each for thermal decomposition and photochemical decomposition reactions. Write balanced equation for the same.

Answer»

Thermal Decomposition: Heating of lime stone

CaCO₃ → CaO+CO₂

Photochemical Decomposition: Action of light on silver bromide.

2AgBr 2Ag + Br₂

Discussion

36.	Correct and balance the following equations :1. Ca + H20 — > CaOH + H 2. N + H — > NH3
Answer» 1. Ca + 2H₂O —–> Ca(OH)₂ + H₂ 2. N₂ + 3H₂ —–> 2NH₃

36.

Correct and balance the following equations :1. Ca + H20 — > CaOH + H 2. N + H — > NH3

Answer»

1. Ca + 2H₂O —–> Ca(OH)₂ + H₂

2. N₂ + 3H₂ —–> 2NH₃

Discussion

37.	Explain the term reactant product giving examples.
Answer» 1. The substance which undergoes bond breaking while taking part in a chemical reaction is called reactant. 2. The substance formed as a result of a chemical reaction by formation of new bonds is called product. 3. Example: In a chemical reaction, the formation of carbon dioxide gas takes place by combustion of coal in air. In this reaction, coal (carbon) and oxygen (from air) are the reactants while carbon dioxide is the product.

37.

Explain the term reactant product giving examples.

Answer»

1. The substance which undergoes bond breaking while taking part in a chemical reaction is called reactant.

2. The substance formed as a result of a chemical reaction by formation of new bonds is called product.

3. Example: In a chemical reaction, the formation of carbon dioxide gas takes place by combustion of coal in air. In this reaction, coal (carbon) and oxygen (from air) are the reactants while carbon dioxide is the product.

Discussion

38.	In which of the following reactions is there only one reactant ? A) combinationB) decomposition C) displacement D) double displacement
Answer» A) combination

Discussion

39.	Write complete balanced equations for the following reactions : (a) Calcium (solid) + Water (liquid) —–> Calcium hydroxide (solution) + Hydrogen (gas) (b) Sulphur dioxide (gas) + Oxygen (gas) —–> Sulphur trioxide (gas)
Answer» (a) Ca (s) + 2H₂O(l) —–> Ca(OH)₂ (aq) + H (g) (b) 2SO₂ (g) + O₂ (g) —–> 2SO₃ (g)

39.

Write complete balanced equations for the following reactions : (a) Calcium (solid) + Water (liquid) —–> Calcium hydroxide (solution) + Hydrogen (gas) (b) Sulphur dioxide (gas) + Oxygen (gas) —–> Sulphur trioxide (gas)

Answer»

(a) Ca (s) + 2H₂O(l) —–> Ca(OH)₂ (aq) + H (g)

(b) 2SO₂ (g) + O₂ (g) —–> 2SO₃ (g)

Discussion

40.	Write the Information conveyed by a chemical equation.
Answer» Information conveyed by a chemical equation 1. Names of various reactants and products 2. Formula of reactants and products 3. Relative number of moles of the reactants and products 4. Relative masses of reactants and products 5. Relative volumes of gaseous reactants and products

40.

Write the Information conveyed by a chemical equation.

Answer»

Information conveyed by a chemical equation

1. Names of various reactants and products

2. Formula of reactants and products

3. Relative number of moles of the reactants and products

4. Relative masses of reactants and products

5. Relative volumes of gaseous reactants and products

Discussion

41.	State the factors which affect the speed (or rate) of a reaction.
Answer» The factors which affect the rate of a reaction are 1. Nature of the reactants. 2. Size of the particles of the reactants. 3. Concentration of the reactants. 4. Temperature of the reaction. 5. Catalyst.

41.

State the factors which affect the speed (or rate) of a reaction.

Answer»

The factors which affect the rate of a reaction are

1. Nature of the reactants.

2. Size of the particles of the reactants.

3. Concentration of the reactants.

4. Temperature of the reaction.

5. Catalyst.

Discussion

42.	Fe2O3 + 2Al ➝ Al2O3 + 2FeThe above reaction is an example of aa) combination reactionb) double displacement reaction.c) decomposition reaction.d) displacement reaction.
Answer» (d) displacement reaction.

Discussion

43.	Fe2O3 + 2Al → Al2O3 + 2FeThe above reaction is an example of aCombination reaction.Double displacement reaction.Decomposition reaction.Displacement reaction.
Answer» Answer is 4. Displacement reaction. Explanation: The Oxygen from the Ferrous oxide is getting displaced to the Aluminium metal to form Aluminium Oxide. In this reaction Aluminum is more reactive metal than Fe. Therefore Al will displace Fe from its oxide. This type of chemical reactions in which one of the elements displace another is called displacement reaction. Here less reactive metal is displaced by more reactive metal. Since one-time displacement is occurring, therefore, it is called a single displacement reaction.

43.

Fe2O3 + 2Al → Al2O3 + 2FeThe above reaction is an example of aCombination reaction.Double displacement reaction.Decomposition reaction.Displacement reaction.

Answer»

Answer is 4. Displacement reaction.

Explanation: The Oxygen from the Ferrous oxide is getting displaced to the Aluminium metal to form Aluminium Oxide. In this reaction Aluminum is more reactive metal than Fe. Therefore Al will displace Fe from its oxide. This type of chemical reactions in which one of the elements displace another is called displacement reaction. Here less reactive metal is displaced by more reactive metal. Since one-time displacement is occurring, therefore, it is called a single displacement reaction.

Discussion

44.	What is a balanced chemical equation? Why should a chemical equation be balanced?
Answer» Chemical Equation: A balanced chemical equation is the symbolic representation of a chemical reaction in which the reactants and products are represented in their symbols with their number of moles involved for complete reaction. A chemical equation is balanced to follow the law of conservation of mass. A balanced equation is the one in which number of different atoms on both the reactant and product sides are equal. Balancing chemical equation is necessary for the reaction should obey The Law of Conservation of energy. Balancing the chemical equation has no defined method and is purely a trial and error attempt.

44.

What is a balanced chemical equation? Why should a chemical equation be balanced?

Answer»

Chemical Equation: A balanced chemical equation is the symbolic representation of a chemical reaction in which the reactants and products are represented in their symbols with their number of moles involved for complete reaction.

A chemical equation is balanced to follow the law of conservation of mass.

A balanced equation is the one in which number of different atoms on both the reactant and product sides are equal. Balancing chemical equation is necessary for the reaction should obey The Law of Conservation of energy. Balancing the chemical equation has no defined method and is purely a trial and error attempt.

Discussion

45.	A balanced chemical equation is appreciable because, it gives A) mass – mass relationship B) mass – volume relationship C) volume – volume relationship D) above all
Answer» D) above all

Discussion

46.	Assertion (A) : All the chemical equations must be balanced. Reason (R) : Atoms are either created or destroyed in chemical reaction. A) Both ‘A’ and ‘R’ are correct and ‘A’ is supported by ‘R’.B) Both ‘A’ and ‘R’ are correct, but ‘A’ is not supported by ‘R’. C) ‘A’ is correct, but ‘R’ is incorrect. D) ‘A’ is incorrect, but ‘R’ is correct.
Answer» C) ‘A’ is correct, but ‘R’ is incorrect.

Discussion

47.	Which information is not conveyed by a balanced chemical equation ? A) Symbols and formulae of all the substances involved in a particular reaction B) Number of atoms / molecules of the reactants and products involved C) Physical states of reactants and products D) Whether a particular reaction is actually possible or not
Answer» D) Whether a particular reaction is actually possible or not

Discussion

48.	All decomposition reactions are endothermic reactions. Give reason.
Answer» Decomposition reactions require energy (either in the form of heat, light or electricity) for breaking down the reactants. Hence, all decomposition reactions are endothermic.

Discussion

49.	Mention a measure which prevents or slows down its oxidation.
Answer» Keeping food in air tight containers / flushing the container with an inert gas like Nitrogen (N₂).

Discussion

50.	What happens when Zn strip is dipped in CuSO4 solution ?
Answer» Zinc strip displaces or removes Copper from Copper sulphate solution and this reaction is known as displacement reactions. Zn(s)+CuSO₄(sq) → ZnSO₄(aq)+Cu(s)

50.

What happens when Zn strip is dipped in CuSO4 solution ?

Answer»

Zinc strip displaces or removes Copper from Copper sulphate solution and this reaction is known as displacement reactions.

Zn(s)+CuSO₄(sq) → ZnSO₄(aq)+Cu(s)

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

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Give an example, each for thermal decomposition and photochemical decomposition reactions. Write balanced equation for the same.

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Explain the term reactant product giving examples.

In which of the following reactions is there only one reactant ? A) combinationB) decomposition C) displacement D) double displacement

Write complete balanced equations for the following reactions : (a) Calcium (solid) + Water (liquid) —–&gt; Calcium hydroxide (solution) + Hydrogen (gas) (b) Sulphur dioxide (gas) + Oxygen (gas) —–&gt; Sulphur trioxide (gas)

Write the Information conveyed by a chemical equation.

State the factors which affect the speed (or rate) of a reaction.

Fe2O3 + 2Al ➝ Al2O3 + 2FeThe above reaction is an example of aa) combination reactionb) double displacement reaction.c) decomposition reaction.d) displacement reaction.

Fe2O3 + 2Al → Al2O3 + 2FeThe above reaction is an example of aCombination reaction.Double displacement reaction.Decomposition reaction.Displacement reaction.

What is a balanced chemical equation? Why should a chemical equation be balanced?

A balanced chemical equation is appreciable because, it gives A) mass – mass relationship B) mass – volume relationship C) volume – volume relationship D) above all

All decomposition reactions are endothermic reactions. Give reason.

Mention a measure which prevents or slows down its oxidation.

What happens when Zn strip is dipped in CuSO4 solution ?

What is wrong with the following chemical equation ?Mg + O ——— > MgOCorrect and balance it.

Correct and balance the following equations :1. Ca + H20 — > CaOH + H 2. N + H — > NH3

Write complete balanced equations for the following reactions : (a) Calcium (solid) + Water (liquid) —–> Calcium hydroxide (solution) + Hydrogen (gas) (b) Sulphur dioxide (gas) + Oxygen (gas) —–> Sulphur trioxide (gas)