1 In an exothermic reaction, what happens to the temperature of the surroundings? A It decreases B It increases C It remains constant D It first increases then decreases
2 In a chemical equilibrium, the rate of forward reaction is: A Greater than the rate of backward reaction B Less than the rate of backward reaction C Equal to the rate of backward reaction D Zero
3 Dynamic equilibrium is reached when: A forward and backward rates become equal B forward reaction stops completely C backward reaction stops completely D concentrations of reactants and products become zero
4 Which statement is true about the equilibrium constant Kc? A It depends on initial concentrations. B It changes with the addition of a catalyst. C It is constant at a given temperature. D It changes with pressure for all reactions.
5 Which of the following is an example of a closed system? A A cup of tea left open B A sealed bottle of water C A boiling pot without lid D A plant in a garden
6 The role of a catalyst in a reversible reaction at equilibrium is to: A increase the yield of products B shift equilibrium to the right C help reach equilibrium faster D change the equilibrium constant
7 According to collision theory, a reaction occurs when reactant molecules collide with sufficient energy and proper ____. A orientation B mass C volume D density
8 For the reaction N2O4(g) ⇌ 2NO2(g), an increase in pressure will shift equilibrium to: A The right B The left C No shift D Stop the reaction
9 A closed system is necessary for dynamic equilibrium because: A reactants cannot be added B products cannot be removed C matter cannot enter or leave D temperature remains constant
10 What does a double arrow (⇌) in a chemical equation show? A The reaction is reversible. B The reaction is irreversible. C The reaction is very fast. D The reaction produces a gas.
11 What happens to the equilibrium constant when a catalyst is added? A It increases B It decreases C It remains unchanged D It becomes zero
12 According to Le Chatelier's principle, increasing the pressure on a gaseous equilibrium will shift the equilibrium towards: A The side with more moles of gas B The side with fewer moles of gas C The reactant side only D No change
13 For the equilibrium PCl5(g) ⇌ PCl3(g) + Cl2(g), increasing the volume of the container will: A shift equilibrium to the left B shift equilibrium to the right C increase the total pressure D have no effect on equilibrium
14 What is enthalpy? A The heat content of a system at constant pressure B The total mass of a system C The volume of a gas D The temperature of surroundings
15 The heat content of a system at constant pressure is called: A Entropy B Enthalpy C Internal energy D Free energy
16 Which of the following statements about an isolated system is correct? A It can exchange both matter and energy. B It can exchange only energy. C It can exchange only matter. D It cannot exchange matter or energy.
17 What is the system in a chemical reaction? A The part of the universe being studied B Everything outside the reaction vessel C Only the solvent D Only the catalyst
18 What is the sign of ΔH for an exothermic reaction? A Positive B Negative C Zero D Depends on temperature
19 For the reaction N2(g) + 3H2(g) ⇌ 2NH3(g), what is the effect of increasing pressure on the equilibrium? A It shifts to the left. B It shifts to the right. C It has no effect. D It changes the equilibrium constant.
20 What is the role of a catalyst in a reversible reaction at equilibrium? A It increases the rate of both forward and backward reactions equally. B It shifts the equilibrium to the forward direction. C It shifts the equilibrium to the backward direction. D It changes the value of the equilibrium constant.
21 Which of the following is an example of a physical equilibrium? A Formation of ammonia from nitrogen and hydrogen. B Melting of ice and freezing of water in a closed system. C Combustion of methane. D Rusting of iron.
22 For the reaction 2SO2(g) + O2(g) ⇌ 2SO3(g), increasing the pressure will: A Shift equilibrium to the left B Shift equilibrium to the right C Have no effect D Decrease the equilibrium constant
23 Which of the following is an isolated system? A A sealed thermos flask B A cup of hot tea C A boiling pot without lid D An open beaker
24 Which change will increase the yield of ammonia in the Haber process? N2(g) + 3H2(g) ⇌ 2NH3(g) + heat A Increase in temperature B Decrease in pressure C Increase in pressure D Adding a catalyst
25 Dynamic equilibrium is established in a closed system when: A forward reaction stops B backward reaction stops C forward and backward rates become equal D concentrations of reactants become zero