Table of Contents
1. Which of the following are Lewis acids?
(a) PH3 and BCl3
(b) AlCl3 and SiCl4
(c) PH3 and SiCl4
(d) BCl3 and AlCl3
Solution:
The compound which can accept a pair of electrons is known as Lewis acid. BCl3 and AlCl3 have vacant orbitals and their octet is not complete. Hence these can accept electron pairs and behave as Lewis acids.
Therefore, option (d) is the correct answer.
2. Species acting as both Bronsted acid and base is
(a) (HSO4) –
(b) Na2 CO3
(c) NH3
(d) OH-
Solution:
A Bronsted acid is a substance that can donate a proton to any other substance and a Bronsted base is a substance that can accept a proton from any other substance. (HSO4)– can donate and accept a proton.
Therefore, option (a) is the correct answer.
3. What is the conjugate base of OH–?
(a) O2
(b) H2O
(c) O–
(d) O-2
Solution:
When acid gives H+ then the remaining of its part is called the conjugate base.
The conjugate base of OH– is O-2.
Therefore, option (d) is the correct answer.
4. Which one of the following substances has the highest proton affinity?
(a) H2S
(b) NH3
(c) PH3
(d) H2O
Solution:
The stability of the conjugate acid will give us the compound with the highest proton affinity.
Here ammonia has the highest proton affinity.
Therefore, option (b) is the correct answer.
5. When rain is accompanied by a thunderstorm, the collected rainwater will have a pH value
(a) slightly lower than that of rainwater without a thunderstorm
(b) slightly higher than that when the thunderstorm is not there
(c) uninfluenced by the occurrence of a thunderstorm
(d) which depends on the amount of dust in the air.
Solution:
The temperature increases due to the thunderstorm. As temperature increases, [H+] also increases, and thus pH decreases.
Therefore, option (a) is the correct answer.
6. For the reaction, 2SO2(g) + O2(g) ⇌ 2SO3(g), ∆H = -57.2 kJ mol–1 and Kc = 1.7 × 1016 Which of the following statements is incorrect?
(a) The equilibrium will shift in the forward direction as the pressure increases.
(b) The addition of inert gas at constant volume will not affect the equilibrium constant.
(c) The equilibrium constant is large, suggestive of reaction going to completion and so no catalyst is required.
(d) The equilibrium constant decreases as the temperature increases.
Solution:
The large value of Kc suggests that the reaction should go almost to completion. The oxidation of SO2 to SO3 is very slow. So the rate of reaction is increased by adding a catalyst. Statement c is wrong.
Therefore, option (c) is the correct answer.
7. 20 mL of 0.1 M H2SO4 solution is added to 30 mL of 0.2 M NH4OH solution. The pH of the resultant mixture is [pKb of NH4OH = 4.7]
(a) 9.4
(b) 9.0
(c) 5.0
(d) 5.2
Solution:
Given pKb of NH4OH = 4.7
20 mL of 0.1 M H2SO4 ⇒ nH+ = 4
30 ml 0.2 M NH4OH ⇒ nNH4OH = 6
Solution is basic buffer.
pOH = pKb + log [NH4+]/[NH4OH] = 4.7 + log (4/2)
= 4.7 + log 2
= 4.7+0.3
= 5
pH = 14-pOH
= 14-5 = 9
Therefore, option (b) is the correct answer.
8. The increase of pressure on the ice water system at constant temperature will lead to
(a) no effect on that equilibrium
(b) a decrease in the entropy of the system
(c) a shift of the equilibrium in the forward direction
(d) an increase in the Gibbs energy of the system.
Solution:
On increasing the pressure on this system in equilibrium, the equilibrium tends to shift in a direction in which volume decreases, i.e., in the forward direction.
Therefore, option (c) is the correct answer.
FAQs
What's the significance here in Chemistry?
In basic terms, Equilibrium alludes to a point wherein a synthetic response has no further changes in the convergence of reactants and items. This state is known as Chemical Equilibrium or just Equilibrium. To put it significantly more just, it is a condition of equilibrium where contradicting powers are counteracting one another so there are no net changes in the centralization of reactants and items.
Weightage of Equilibrium in JEE Main?
The weightage of the section on Equilibrium is normally around 6-7 per cent. This really intends that something like 2 inquiries will in all likelihood come from this part, so it's ideal to get ready for it since the science segment is the segment that is generally simple to score in.
