This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Chemical Equilibrium”.
1. Why do buffer solutions have constant acidity and alkalinity?
a) They have fixed pH value
b) These give unionized ions on reaction
c) They have large excess of H+ or OH–
d) Acids and alkalis are shielded from other ions
View Answer
Explanation: In a buffer solution, a small quantity of acid or base added from outside try to maintain pH value. They have constant acidity and alkalinity because of unionized acid or base on reaction with added acid or alkali.
2. What is a chemical equilibrium?
a) State in which both reactants and products are present in concentration which does not change with time
b) Total entropy can only increase over time
c) It is the relation between the heat and other forms of energy
d) Change for the formation of one mole of compound from their elements in most stable states
View Answer
Explanation: Chemical equilibrium is a state in which both reactants and products are present in the concentration which does not change with time. It occurs when a reversible reaction is occurring backward and forward at the same time.
3. The Equilibrium constant is the value of reaction when the reaction has not reached equilibrium.
a) True
b) False
View Answer
Explanation: It is the value of reaction when the reaction has reached its equilibrium. Its value is independent of the analytical concentration of the reactant and product.
4. Amines behave as Lewis base.
a) True
b) False
View Answer
Explanation: Amines behave as Lewis base because it can provide the free electron pair. A Lewis base is a species which can donate an electron pair.
5. The concentration of products and reactants will be same if _________
a) Volume is not constant
b) Viscosity is constant
c) Pressure is not constant
d) Temperature is constant
View Answer
Explanation: If the forward rate and reverse rate are equal, the concentration of the product and reactants will be same.
6. Water flows over a waterfall 100 m in height. Take 1 kg of the water as the system, and assume that it does not exchange energy with its surroundings. What is the potential energy of the water at the top of the falls with respect to the base?
a) 244.90 J
b) 500.88 J
c) 798.32 J
d) 980.66 J
View Answer
Explanation: Δ (Energy of the surroundings) = ΔU + ΔEK + ΔEP = 0
EP = m*z*g = 1kg * 100 * 9.8066 ms-2
= 980.66 kg m2/s2 = 980.66 Nm = 980.66 J
7. Calculate the degree of freedom for liquid water in equilibrium with its vapor.
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The system contains a single chemical species existing as two phases. Thus, F = 2 – π + N = 2 – 2 +1 =1.
8. Calculate the degree of freedom for liquid water in equilibrium with a mixture of water vapor and nitrogen.
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: In this case two chemical species are present. Again, there are two phases: F = 2 – π + N = 2 – 2 + 2 = 2.
9. For the flow of calorimeter, the following data is given: Flow rate = 4.15 gs-1, t1/T1 = 0℃/273.15 K, t2/T2 = 300℃/573.15 K, P2 = 3 bar, Rate of the heat of addition = 12740 W. Calculate the enthalpy of steam at 300℃.
a) 3070 J g-1
b) 4070 J g-1
c) 5070 J g-1
d) 6070 J g-1
View Answer
Explanation: If z and u2 are negligible and if Ws and H1 are zero, then H2 = Q and H2 = 12740/4.15 = 3070 J g-1.
10. Waterfall height = 100m. Take 1 kg of the water as the system. Calculate the kinetic energy of the water just before it strikes bottom?
a) 980.66 J
b) 880.77 J
c) 456.90 J
d) 789.09 J
View Answer
Explanation: During the free fall of the water no mechanism exists for conversion of potential or kinetic energy into internal energy. Thus, ΔU must be zero: ΔEK + ΔEP = EK2 – EK1 – EP1 = 0. Let EK1 = EP2 = 0. Then, EK2 = EP1 = 980.66 J.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
To practice all areas of Physical Chemistry, here is complete set of Multiple Choice Questions and Answers.
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