Food Processing Unit Operations Problems on “Equilibrium Concentration Relationship”.
1. What is equilibrium constant expression?
a) The ratio of the concentrations of the reactants and molar constant and products
b) The ratio of the concentrations of the products and reactants
c) The ratio of the concentrations of the reactants and products
d) The ratio of the concentrations of the catalyst and products
Answer: c
Clarification: The ratio of the concentrations of the reactants and products is called as equilibrium constant expression. When the reaction reaches equilibrium, the association between the concentrations of the reactants and products termed by the equilibrium constant expression is always same.
2. How does increase in concentration affect equilibrium?
a) It will shift towards the products.
b) It will shift towards the reactants.
c) No change
d) It will shift according to pressure change
Answer: a
Clarification: When there is increase in concentration the equilibrium will shift towards the products. There will be increase in product formation and there will be decrease in concentration of the reactants as the concentration of the products increases.
3. What affects equilibrium?
a) Changes in concentration
b) Changes in and pressure
c) Changes in temperature
d) Changes in concentration, temperature, and pressure
Answer: d
Clarification: Changes in concentration, temperature, and pressure can affect the position of equilibrium of a reversible reaction. If the forward reaction is endothermic, then there is an increase in temperature that causes the system to shift toward the products.
4. Do catalysts affect equilibrium?
a) True
b) False
Answer: b
Clarification: The catalyst speeds up the forward and back reaction to the same extent and addition of a catalyst does not affect the relative rates of the two reactions and cannot affect the position of equilibrium.
5. What is the relation between Kp and K?
a) Kp=K(RT)Δn
b) Kp=K-(RT)Δn
c) Kp=K+(RT)Δn
d) Kp=K/(RT)Δn
Answer: a
Clarification: The relation between Kp and K is Kp=K(RT)Δn. An equilibrated system that contains products and reactants in a single phase is a homogeneous equilibrium where as a system whose reactants, products are in more than one phase, it is called as heterogeneous equilibrium.
6. The equilibrium constant for the reaction of nitrogen and hydrogen to give ammonia is 0.95 at 745 K. The balanced equilibrium equation is as follows:
N2(g)+3H2(g)⇌2NH3(g)
What is Kp for this reaction at the same temperature?
a) 2.54×10-4
b) 3.85×10-4
c) 4.27×10-4
d) 3.73×10-4
Answer: a
Clarification: This reaction has 2 moles of gaseous product and 4 moles of gaseous reactants, so Δn=(2−4)=−2. We know K, and T=745K.
Kp=K(RT)−2
0.95 x {[0.08206(L⋅atm)/(mol⋅K)][745K]}-2 = 2.54×10-4.
7. What is use of law of mass action in equilibrium?
a) Predicts behaviors of solutions in dynamic equilibrium
b) To calculate the concentration of products
c) To calculate the concentration of reactants
d) Predicts behaviors of solutes
Answer: a
Clarification: Law of mass action in equilibrium predicts behaviors of solutions in dynamic equilibrium. The law of mass action defines that the rate of the chemical reaction is directly proportional to the product of the activities or the reactants concentration.
8. Who discovered law of mass action?
a) Guldberg and Waage
b) Newton
c) Henricus
d) Gyarmati
Answer: a
Clarification: Guldberg and Waage recognized that chemical equilibrium is a dynamic process where rates of forward reactions and rate of backward reactions must be equal at chemical equilibrium.
9. Are these statements about the Equilibria involving physical processes true?
Statement 1: Equilibrium is possible only in an open system.
Statement 2: All measurable properties of the system remain constant.
a) True, False
b) True, True
c) False, True
d) False, False
Answer: c
Clarification: Equilibrium is possible only in a closed system. All measurable properties remain constant of the system. Both the opposing processes occur at the same rate. It is a dynamic state but stable condition.
10. Is equilibrium mean equal concentrations?
a) True
b) False
Answer: b
Clarification: Equilibrium does not essentially mean that substances present are in equivalent amounts. It is defined that the reaction has reached to a point where the reactant’s concentrations and product’s concentration are static with time and the forward and backward reactions have the equal rate.
Food Processing Unit Operations Problems,