IB myp 4-5 Chemistry – Practice Questions- All Topics
Topic :Bonding–equilibria/reversible reactions
Topic :Bonding- Weightage : 21 %
All Questions for Topic :structure and bonding,properties,chemical formulas,chemical reactions and the conservation of mass; balancing,equations, the mole concept and chemical calculations;
reaction kinetics [rates, and factors affecting rates/collision theory],equilibria/reversible reactions,energy changes in reactions, endo- and exothermicity; combustion of fuels)
Summative assessment
Le Chatelier’s principle
Le Chatelier’s principle states that if a system in equilibrium is disturbed by changes in temperature, pressure, and/or concentration of the components, the system will shift the position of the
equilibrium to counteract the change and return the system to balance.
For each of the following chemical reactions, examine the reactants and products and their states of matter, and decide how the change in reaction conditions will affect the position of the equilibrium.
Question:
The Haber process describes the industrial production of ammonia gas on a large scale:
N2(g) + 3H2(g) ⇔2NH3(g) ΔH° = –92 kJ mol–1
Predict the effect of the following changes on the position of the equilibrium in the Haber process.
a) Nitrogen gas is added to the system at equilibrium.
▶️Answer/Explanation
Ans: The forward reaction is favored.
b) Hydrogen gas is removed from the system at equilibrium.
▶️Answer/Explanation
Ans: The reverse reaction is favored.
c) The pressure of the system is decreased.
▶️Answer/Explanation
Ans: In this reaction, there are 4 moles of reactant gases and 2 moles of product gases; a decrease in pressure will favor the side with the greatest number of moles of gas, therefore the reverse reaction is favored.
d) The temperature of the system is increased.
▶️Answer/Explanation
Ans: The reaction is an exothermic reaction; therefore an increase in temperature will favor the reverse reaction.
Question:
The decomposition of sulfur trioxide is an endothermic process:
2SO3(g) 2SO2(g) + O2(g) H° = +196 kJ mol–1
Predict the effect of the following changes on the position of the equilibrium:
a) Sulfur trioxide gas is removed from the system at equilibrium.
▶️Answer/Explanation
Ans: The reverse reaction is favored.
b) Oxygen gas is removed from the system at equilibrium.
▶️Answer/Explanation
Ans: The forward reaction is favored.
c) The pressure of the system is increased.
▶️Answer/Explanation
Ans: In this reaction, there are 2 moles of reactant gases and 3 moles of product gases; an increase in pressure will favor the side with the least number of moles of gas, therefore the reverse reaction is favored.
d) The temperature of the system is decreased.
▶️Answer/Explanation
Ans: The reaction is an endothermic reaction; therefore a decrease in temperature will favor the reverse reaction.