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(i) I₂ < F₂ < Br₂ < Cl₂

(ii) BiH₃ <SbH₃ < AsH₃ < PH₃ < NH₃

1. neutralization 

2. H₂ 

3. physical equilibrium 

4. increases to ‘7’ 

5. 1 × 10^-14 mol² dm^-6 

6. 7.4

7. decomposition 

8. 1 

9. decomposition 

10. hydronium ion

A combination reaction is a reaction in which two or more reactants combine to form a compound. 

Eg: C_(s) + O_2(g) → CO_2(g) + heat

1. False – Silver cannot displace H₂ from HNO₃ acid, since it is placed below hydrogen in the activity series. 

2. True 

3. False – At equilibrium the concentration of the reactants and products do not change it remains constant, but the concentration of the reactants and the products will not be equal. 

4. True 

5. False – The solution is neutral if the solution is basic it will be green in colour.

Chemical equilibrium is a state of a reversible chemical reaction where the, 

Rate of forward reaction = Rate of backward reaction. 

No change in the amount of the reactants and products takes place.

Characteristics of equilibrium: 

1. In a chemical equilibrium, the rates of the forward and backward reactions are equal. 

2. The observable properties such as pressure, concentration, colour, density, viscosity etc., of the system remain unchanged with time. 

3. The chemical equilibrium is a dynamic equilibrium, because both the forward and backward reactions continue to occur even though it appears static externally. 

4. In physical equilibrium, the volume of all the phases remain constant.

• The pH of blood is almost 7.4. Any increase or decrease in this value leads to diseases 
• Citrus fruits require slightly alkaline soil, while rice requires acidic soil and sugarcane requires neutral soil. 
• If the pH of rainwater becomes less than 7, it becomes acid rain which is harmful in day-to-day life. 
• pH changes cause tooth decay. 
• During indigestion, the stomach produces too much acid and this causes pain and irritation.

On increasing temperature heat is supplied to the reactant. This energy breaks more bonds and thus speed up the chemical reaction. Foods kept at room temperature spoils faster than that kept in the refrigerator

A. (iii) 

B. (i) 

C. (iv) 

D. (ii)

Important factors that affect rate of a reaction are: 

1. Nature of the reactants 

2. Concentration of the reactants 

3. Temperature

4. Catalys

5. Pressure 

6. Surface area of the reactants

1. Nature of the reactants : 

The reaction of sodium with hydrochloric acid is faster than that with acetic acid, because Hydrochloric acid is a stronger acid than acetic acid and thus more reactive. So, the nature of the reactants influence the reaction rate.

2Na_(s) + 2HCl_(aq) → 2NaCl_(aq) + H_2(g) (fast)

2Na_(s) + 2CH₃COOH_(aq) → 2CH₃COONa_(aq) + H_2(g) (slow)

2. Concentration of the reactants : 

Changing the amount of the reactants also increases the reaction rate. More the concentration, more particles per volume exist in it and hence faster the reaction. Granulated zinc reacts faster with 2M hydrochloric acid than 1M hydrochloric acid. 

3. Temperature : 

Most of the reactions go faster at higher temperature. Because adding heat to the reactants provides energy to break more bonds and thus speed up the reaction. Calcium carbonate reacts slowly with hydrochloric acid at room temperature. When the reaction mixture is heated the reaction rate increases.

4. Pressure : 

If the reactants are gases, increasing their pressure increases the reaction rate. This is because, on increasing the pressure the reacting particles come closer and collide frequently. 

5. Catalyst : 

A catalyst is a substance which increases the reaction rate without being consumed in the reaction. In certain reactions, adding a substance as catalyst speeds up the reaction. 

For example, on heating potassium chlorate, it decomposes into potassium chloride and oxygen gas, but at a slower rate. If manganese dioxide is added, it increases the reaction rate.

6. Surface area of the reactants :

Powdered calcium carbonate reacts more readily with hydrochloric acid than marble chips. Because, powdering of the reactants increases the surface area and more energy is available on collision of the reactant particles. Thus, the reaction rate is increased.

KOH → K⁺ + OH^- 

pOH = -log[OH^-]

= -log [1 × 10^-5] 

pOH = 5

pH + pOH = 14 

∴ pH of KOH = 14 – 5 = 9 

pH = 9

(a) Thermolysis

(c) mol dm^-3

pH = 8.5

pH = – log [H⁺]

[H⁺] = 10^-pH

[H⁺] = 10^-8.5

[H⁺] = 3.16 × 10^-9 M

(a) compound to element/element

(b) Photolysis

(c) light

2AgBr_(s) + Light ⟶ 2Ag_(s) + Br_2(g)

(c) 1 × 10^-11 M 

It means [H⁺] = 10^-3

[H⁺] [OH^-] = 10^-14 

[10^-3] [OH^-] = 10^-14 

[OH^-] = 10^-11

 (iii) 8×10⁴ Nm^–2

[OH^-] = 1 × 10^-11 M

pOH = – log[OH^-]

= – log[1 × 10^-11] 

= -log₁₀1 – log₁₀10^-11

= -(-11) log₁₀10 = 11

pOH = 11

pH + pOH = 14

pH = 14 – 11

pH = 3

(d) all the above

When the same volume of another gas is introduced in the same room, i.e., the volume remains constant, then

No. of moles = n + n = 2n (equal volume contains equal no. of moles)

Total pressure = (p + p) atm = 2p atm (increases due to addition of another gas)

Temperature = t°C (unchanged)

Density = 2 ρ g cm^-3 (gets doubled)

(a) Stabilty of higher oxidation state decrease down the group from S to Te/stability of lower oxidation state increases down the group from S to Te.

(b) ClO₃ is more stable than ClO^-/ClO₃^-  is weak conjugate base than ClO^-/Due to higher oxidation state of chlorine in HClO₃

(c) Fluorine and oxygen are most electronegative and very reactive.

Fluorine has no d-orbital for excitation of electrons and it is most electronegative element. Hence it shows oxidation state of -1 only.

F₂ is the stronger oxidising agent than chlorine

(a) Low enthalpy of dissociation of F-F bond.

(b) Less negative electron gain enthalpy of F.

(c) High hydration enthalpy of F^- ion

The type of flow in which there is a regular gradation of velocity in passing from one layer to the next is called laminar flow.

1. Of the two acids ‘A’ and ‘B’, ‘A’ is a weak acid and ‘B’ is a strong acid. 

2. A weak acid is the one which ionises partially when dissolved in water.

3. A strong acid is the one which ionises completely when dissolved in water.

4. Weak acid – Acetic acid(CH₃COOH) 

Strong acid – Sulphuric acid (H₂SO₄)

The pH of rain water is approximately ‘7’ but when the air is polluted with oxides of S and N, they get dissolved in the rain water and make its pH less than 7, then it is called acid rain.

(d) high temperature

(i) pH = -log[1 × 10^-8]

pH = 8

(ii) pOH = 14 – 8 

= 6

(iii) Acidic

(i)  pH = -log[1 × 10^-8]

PH = 8

(ii) pOH = 14 – 8 

= 6

(iii) Acidic

Since HCl is a strong acid, it dissociates

HCl → H⁺ + Cl^- 

[H⁺] = [HCl] = 0.001 M

[H⁺] = 1 × 10^-3 M

pH = -log[H⁺]

= -log[1 × 10^-3]

pH = 3

pH = 5.5

Since pH + pOH = 14

pOH = 14 – pH

= 14 – 5.5 = 8.5

[OH^-] = 10^-POH 

= 10^-8.5 

= 3.16 × 10^-9 M

(OR)

[OH^-] = antilog[-8.5]

= 3.16 × 10^-9 M

[OH^-] = 3.16 × 10^-9 M

(a) Number of moles of O₂

= \(\frac{Mass\,of\,O_2}{Molar\,mass\,of\,O_2}\) = \(\frac{4}{32}\) = 0.125

= \(\frac{Mass\,of\,H_2}{Molar\,mass\,of\,H_2}\) = \(\frac{2}{2}\) = 1

Total moles = 0.125 + 1 = 1.125

According to ideal gas equation, -

PV = nRT

[V = 1 L, n = 1.125 moles, T = 0 + 273 = 273 K, P =?]

\(\therefore\) P = \(\frac{nRT}{V}\)

= \(\frac{1.125\,moles\times0.0821\,L\,atm\,K^{-1}mol^{-1}\times273\,K}{1\,L}\)

= 25.215 atm

(b) At SATP, the molar volume of a gas is 24.789 L mol^-1

(c) Gay Lussac's Law: According to this law, “At constant volume, pressure of a fixed amount of a gas varies directly with the temperature." Mathematically, P \(\propto\) T

Or \(\frac{P}{T}\) = = constant = K

(i) SO₂ is reducing agent as sulphur has d-orbital so it can easily expand its + 4 oxidation state to f 6 oxidation state and acts as reducing agent while in Te oxidation number changes from O to + 4 and electrons are reluctant to take part in bond formation due to poor shielding of d- and f -orbital. Thus lower oxidation state (+2, -2) becomes more stable and therefore TeO₂ is oxidizing agent.

(ii) Formation of pentahalides requires sp³d hybridization of the central atom obtained by the excitement of electrons of the central atom to empty d-orbitals. As nitrogen has no d-orbital it cannot undergo sp³d hybridization and therefore cannot form pentahalides.

(iii) Inter halogen compound ICI are more reactive than halogens CI₂ because X-X (I - Cl) bond in inter halogens is weaker than Cl-Cl bond in halogens except F-F bond.

(i) In the sealed aerated soft drink bottle, the dissolved CO₂ , in the form of carbonic acid and gaseous CO₂ are in equilibrium.

(ii) When we open the bottle the gaseous CO₂ will escape and the dissolved CO₂ begins to undissolve to the gas phase to maintain the equilibrium. So when we keep the bottle open for a long time it will go flat with all the dissolved CO₂ gone.

When a liquid is heated up to its critical temperature in a closed vessel, it does not pass through a two phase region and substances remain in one phase. There is a continuity between a gaseous and liquid state. The term fluid is used for either a liquid or a gas to recognize this continuity. Liquid and gas can be distinguished only when the fluid is below its critical temperature and the surfaces separating them can be seen. At critical temperature, liquid passes into gaseous state continuously and the surface separating the two phases disappears. A gas below the critical temperature can be liquefied by applying pressure.

W_O2 = 4g

∴ Moles of O₂ = (4/32) = (1/8)

W_H2 = 2g

∴ Moles of H₂ = (2/2) = 1

Total moles present in mixture = (1/8 + 1) = 9/8

Volume of vessel = 1 litre

Temperature = 273 K

Now for pressure of mixture, p x v = nRT

p x 1 = (9/8) x 0.0821 x 273

∴ p = 25.215 atm.

Sodium fluoride > Zinc iodide > Naphthalene > Phosphorus > Water.

On heating the glass it melts and take up rounded shape at edges which has minimum surface area. b/c of surface tension. 

On heating the glass, it melts and takes up rounded shape at the edges which has minimum surface area. This is due to the property of surface tension of liquids.

In aerated water bottles, CO₂ gas is passed through the aqueous solution under pressure because the solubility of the gas in water is not very high. In summer, the solubility of the gas in water is likely to decrease because the rise in temperature decreases the solubility. Thus, in summer, more of gas will be present above the liquid surface in the glass bottle. In case, the pressure of the gas becomes too high, then glass will not be able to withstand the pressure. The bottle may explode and may lead to serious accident. To avoid this, the bottles are kept under water. As a result, the temperature is likely to decrease and the solubility of the gas is likely to increase in aqueous solution resulting in decreased pressure.

Impurities affect surface tension appreciably. It is observed that the impurities which lead to concentrate on the surface of the liquid as compared to the bulk, lower the surface tension. Substances like alcohols, soaps, detergents, etc. lower the surface tension of water. Inorganic impurities, e.g. NaCl etc. tend to increase the surface tension of water.

Urea is a crystalline solid while glass is an amorphous solid.

Liquid ammonia bottle contains the gas under very high pressure. If the bottle is opened as such then the sudden decrease in pressure will lead to a large increase in the volume of the gas. As a result, the gas will come out of the bottle all of a sudden with force. This will lead to the breakage of the bottle and also some serious accident. However, if the bottle is cooled under tap water for some time, this will lead to a decrease in the volume of the gas to a large extent. If the seal is opened now, the gas will come out of the bottle at a slow rate. It reduces the chances of accident.

Surface tension decreases with rise in temperature.

(i) As we go to higher altitudes, the atmospheric pressure decreases. Then the pressure outside the balloon decreases. To regasm equilibrium with the external pressure, the gas inside expands to decrease its pressure. Hence, the size of the balloon increases. 

(ii) In summer, due to higher temperature, the average kinetic energy of the air molecules inside the tyre increases, ie., molecules start moving faster. Hence, the pressure on the walls of the tube increases. Its pressure inside is not kept low at the time of inflation, at higher temperature, the pressure may become so high that the tyre may burst.

(a) At higher altitudes, atmospheric pressure decreases, therefore, air inside the weather balloon exerts pressure and its size becomes larger and larger as it ascends higher and higher. 

(b) Copper is metal and has strong metallic bond, that is why it is malleable and ductile. Sulphur is non-metal and has weak intermolecular force of attraction therefore it is brittle.

NH₃ is liquified at high temperature and pressure. It is cooled so as to reduce temperature so that it does not burst.

Viscosity of the liquid is responsible for this.