Explore topic-wise InterviewSolutions in Current Affairs.

H⁺/H₃O⁺and OH^- respectively.

(a) An alloy is a homogeneous mixture of two or more metals (or a metal and small amount of non-metals). An alloy is prepared by mixing the various metals in molten state in required proportions, and then cooling their mixture to the room temperature.

(b) Steel contains iron and carbon. This alloy of iron (steel) is hard and strong. It also rusts less readily than pure iron.

(c) Brass contains copper and zinc. Brass is used for making cooking utensils.

The velocity of sound in air at 25°C is approximately 346 m/sec.

Li₂CO₃ is thermally unstable because it is covalent.

c. amplitude

The silver articles combine slowly with the hydrogen sulphide gas present in air to form a black coating of silver sulphide. The tarnishing of the silver objects is due to this silver sulphide coating on the object’s surface.

(i) Presence of air (oxygen).

(ii) Presence of water (or moisture).

A pleasant sound like Hello sir/Hello madam while addressing a person or hearing musical notes are boon and a loud sound may cause irritation, headache and loss of concentration. Long exposure to such sounds may lead to loss of sleep, tension and stress, high blood pressure, heart trouble etc. Therefore such sounds are bone to us.

The product of frequency and wave length of a sound waves is called velocity.

(a) Sodium.

(b) White phosphorus.

a. sound waves get absorbed by the objects in the hall.

An alloy is a homogenous mixture of two or a metal and non-metal.

Alloys are homogeneous mixture of two or more metals or a metal and a non-metal that cannot be separated into their components by physical methods.

(i) The electrical conductivity.

(ii) Melting point of an alloy is less than that of a pure metal.

e.g., Brass and Bronze are not good conductors of electricity whereas copper is used in making electrical circuit.

e.g., solder has a low melting point.

(a) Covalent bond

(b) Low melting point

(c) No

(d) Yes

(a) When non-metals react with oxygen, they form acidic oxides or neutral oxides.

Example: Carbon reacts with oxygen to form an acidic oxide called carbon dioxide. Hydrogen reacts with oxygen

(b)When metals combine with oxygen, they form basic oxides.

Example: Sodium reacts with oxygen to form a basic oxide called sodium oxide.

(a) Refer to the question No.

Advantages :

(i) to protect the metal from corrosion.

(ii) to improve the quality.

(b) X - Al; Y- Al₂O₃

Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O

Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂

Two ways to prevent the rusting or iron are
(a) Applying oil, paint and grease we can prevent rusting.
(b) By coating with zinc to iron, we can prevent using. This is called Galvanisation.

(a) Barium oxide

(b) Sodium hydroxide

(c) Manganese oxide

(d) Cupper hydroxide

(e) Carbonic acid

(f) Ferric hydroxide

(g) Copper oxide

(h) Ammonia

(i) Ammonium hydroxide

The distance between two successive compression is called wave length of sound wave. This is equal to the distance between two successive rare faction. The wave length is represented by Lambda (‘A’).

The reflection of sound is called Echo.

The highest displacement of a particle from its rest position is the amplitude of the sound.

Sodium, Potassium and Lithium are highly reactive metals. These metals react so vigorously that they catch fire if kept in the open. Hence to protect them and to prevent accidental fire, they are kept immersed in kerosene oil.

When non metals combine with oxygen, neutral oxides or Acidic oxides are formed.

Eg: NO₂, SO₄ are acidic oxides NO, CO are neutral oxides.

Steel – Iron and carbon.

Stainless steel – Iron, chromium and nickel.

Silver metal becomes black in the presence of hydrogen sulphide gas in air .

Some sound cause disturbance to human and other animals, such unwanted sound is called Noise, or Unpleasant sound is called Noise [High frequency sound].

Silver, gold and platinum are used to make jewellery b ecause all of these metals have a bright shiny surface and are resistant to corrosion.

Platinum, gold and silver are used to make jewellery because they are shining metals and less reactive and they do not corrode easily.

We are given that the atomic mass of oxygen is 16u. In a molecule of oxygen, there are two oxygen atoms and it is denoted by O₂. So, the molecular mass of O₂ will be 2 x 16u = 32u. 

Thus, the molar mass that is the mass of 6.023 x 10²³ molecules of oxygen will be 32g. So

mass of 6.023 x 10²³ molecules (one mole) of oxygen = 32g

mass of one molecule of oxygen = [32 /(6.023 x10²³) ]g 

= 5.313 x 10^-23g

Thus, the mass of one oxygen molecule will be 5.313 x 10^-23g 

Zinc is more reactive than tin. Which may react with food items and make it unfit for health.

Zinc is much more reactive as compared to tin and can react with natural acids and bases in food materials. Therefore food cans are made up of tin and not zinc.

1. Platinum, gold and silver are used to make jewellery because of their bright shiny surface and high resistance to corrosion. Also they have high malleability and ductility.

2. Sodium, potassium and lithium are stored under oil to prevent their reaction with oxygen, moisture and carbon dioxide of air so as to protect them as they are highly reactive metals.

3. Aluminium metal forms a thin layer of aluminium oxide all over its surface under the action of moist air. This layer prevents the metal underneath from further corrosion. It is cheap, easily available, malleable and ductile. Therefore, it is used to make utensils for cooking.

Correct option is B) blue

1. The object to be electroplated should be free from greasy matter. 

2. The surface of the article should be rough so that the metal deposited sticks permanently.

3. The concentration of the electrolyte should be so adjusted as to get smooth coating. 

4. Current must be the same throughout.

Insert the wires into a potato. A greenish spot is seen on potato at one of the wires. That wire behave like positive terminal and the other is negative terminal.

(a) Platinum, gold, and silver are used to make jewellery because they are very lustrous. Also, they are very less reactive and do not corrode easily.
(b) Sodium, potassium, and lithium are very reactive metals and react very vigorously with air as well as water. Therefore, they are kept immersed in kerosene oil in order to prevent their contact with air and moisture.
(c) Though aluminium is a highly reactive metal, it is resistant to corrosion. This is because aluminium reacts with oxygen present in air to form a thin layer of aluminium oxide. This oxide layer is very stable and prevents further reaction of aluminium with oxygen. Also, it is light in weight and a good conductor of heat. Hence, it is used to make cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction because metals can be easily extracted from their oxides rather than from their carbonates and sulphides.

Answer: Differences between metals and non-metals on the basis of their chemical properties.

Flow of charged particles constitutes current. So for the passage of current the material should have charged particles. All the materials do not have charged particles, e.g. Plastic, wood, diamond, etc. So only those material which have charged particles allow passage of current.

a) There is red mass of copper deposited on iron key.

b) If we want to coat aluminium or zinc or iron then, we have to take electrolyte is like aluminium sulphate or zinc sulphate and the positive electrode is aluminium or zinc.

Correct option is A) negative

Copper reacts with moist carbon dioxide in air to form copper carbonate and as a result, copper vessel loses its shiny brown surface forming a green layer of copper carbonate. The citric acid present in the lemon or tamarind neutralises the basis copper carbonate and dissolves the layer. That is why, tarnished copper vessels are cleaned with lemon or tamarind juice to give the surface of the copper vessel its characteristic lustre.

a) Acid solutions.

b) Yes, it is useful.

c) After a few seconds of immersion of zinc and copper into dilute sulphuric acid, zinc slowly begins to dissolve in the sulphuric acid. We can see bubbles getting formed on the copper rod. The current is passed from copper rod to zinc rod. Here chemical energy is converted into electric energy by electrolysis method.

d) In the above cell electrolyte is dilute sulphuric acid whereas in dry cell ammonium chloride paste is electrolyte. The electrodes in above cell is copper and zinc, whereas in dry cell it is graphite (carbon) and zinc.

e) Dry cell is better than ordinary Volta cell. The reason dry cell does not have any fluids. So it is easy to carry dry cell compared with volta cell. So dry cell is better than volta cell.

In tarnished copper vessel there is a layer formed due to Corrosion which is basic in nature which get dissolved in the lemon or tamarind juice which are acidic in nature. Copper reacts with moist carbon dioxide in air to form copper vessel which loses its shiny brown surface forming a green layer of copper Carbonate. The Citric acid present in the lemon dissolves this layer and clean the copper vessel.

In order to deflect the needle the liquid must be a good conductor of electricity. So we have to take liquids like lemon juice, vinegar solution, salt solution.

Liquid A is better conductor than liquid B.

Correct option is B) Insulator

Correct option is A) electrolysis

Correct option is C) electroplating

Correct option is B) electroplating

1. Chromium has a shiny appearance does not corrode and resist scratches. 

2. However chromium is expensive and may not be possible to make the whole object out of chromium. 

3. So the object is made from a cheaper metal and only a coating of chromium is done over it.