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)
Question (10 marks)
Cola is a popular soft drink that contains dissolved carbon dioxide gas, which creates bubbles. Originally made from kola nuts, it was first sold as a headache and indigestion remedy.
Question a (1 mark)
State why the gas is named carbon dioxide rather than carbon oxide.
▶️Answer/Explanation
Answer:
Because it contains two oxygen atoms bonded to one carbon atom (CO2).
Explanation:
The prefix “di-” in dioxide indicates two oxygen atoms, following IUPAC naming conventions for covalent compounds.
Question b (1 mark)
State the chemical formula of carbon dioxide.
▶️Answer/Explanation
Answer:
CO2
Explanation:
The formula shows one carbon atom covalently bonded to two oxygen atoms.
Question c (3 marks)
Draw the Lewis (electron dot) structure of carbon dioxide.
▶️Answer/Explanation
Answer:
O::C::O (with double bonds between C and each O)
Explanation:
Carbon shares two electron pairs with each oxygen atom to complete their octets, forming a linear molecule.
Question d (2 marks)
Represent the equilibrium between dissolved CO2 in cola and gaseous CO2 in the headspace using state symbols.
▶️Answer/Explanation
Answer:
CO2(aq) ⇌ CO2(g)
Explanation:
The equation shows the dynamic equilibrium between aqueous CO2 (dissolved in liquid) and gaseous CO2 in the space above the drink.
Question e (3 marks)
Explain what happens to dissolved CO2 concentration when a cold cola can is opened on a warm day.
▶️Answer/Explanation
Answer:
• CO2 solubility decreases with temperature
• Gas escapes as bubbles when pressure is released
• Dissolved concentration decreases over time
Explanation:
Henry’s Law explains that gas solubility decreases with temperature increase and pressure decrease, causing CO2 to come out of solution.
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.