IB Chemistry Review Pre Exam

Which of the following is (are) important in determining whether a reaction occurs?

I. Energy of the molecules

II. Orientation of the molecules

• I only

• II only

• Both I and II

• Neither I or II

The rate of a reaction between two gases increases when the temperature is increased and a catalyst is added. Which statements are both correct for the effect of these changes on the reaction?

• Increasing the temperature causes collision frequency to increase and adding a catalyst causes activation energy to increase

• Increasing the temperature causes activation energy to increase and adding a catalyst does not cause any change in activation energy

• Increasing the temperature doesn't cause any change in activation energy and adding a catalyst causes activation energy to decrease

• Increasing the temperature causes activation energy to increase and adding a catalyst increases collision frequency

Which of the quantities in the enthalpy level diagram below is (are) affected by the use of a catalyst?

• I only

• III only

• I and II only

• II and III only

What changes occur when the temperature is increased in the following reaction at equilibrium?

Br₂(g) + Cl₂(g) ↔ 2BrCl(g) ΔH = +14 kJ/mol

• Equilibrium shifts towards the reactants and the equilibrium constant decreases

• Equilibrium shifts towards the reactants and the equilibrium constant increases

• Equilibrium shifts toward the products and the equilibrium constant decreases

• Equilibrium shifts toward the products and the equilibrium constant increases

What is the equilibrium constant expression, K_c, for the following reaction?

N₂O₄(g) ↔ 2NO₂(g)

• K_c = [NO₂]/[N₂O₄]

• K_c = [NO₂]²/[N₂O₄]

• K_c = [NO₂]/[N₂O₄]²

• K_c = [NO₂][N₂O₄]²

Which statement is correct for a crystal of iron(II) sulfate in a state of equilibrium with a saturated solution of iron(II) sulfate?

• The color of the solution darkens as the crystal continues to dissolve

• The concentration of the iron(II) sulfate solution increases as the water evaporates

• The shape of the iron(II) sulfate crystal does not change

• the color of the solution does not change but the shape of the crystal may change

According to the reaction below, what temperature and pressure conditions will produce the greatest amount of SO₃?

2SO₂(g) + O₂(g) ↔ 2SO₃(g) ΔH = -200 kJ

• Low temperature and low pressure

• Low temperature and high pressure

• High temperature and high pressure

• High temperature and low pressure

Which statement concerning a chemical reaction at equilibrium is not correct?

• The concentrations of reactants and products remain constant

• Equilibrium can be approached from both directions

• The rate of the forward reaction equals the rate of the reverse reaction

• Changing the temperature does not affect the value of the equilibrium constant

Which substance, when dissolved in water, to give a 0.1 mol/dm³ solution, has the highest pH?

• HCl

• NaCl

• NH₃

• NaOH

What is the formula for the conjugate base of the hydrogenphosphate ion, HPO₄^2-?

• H₂PO₄^-

• H₃PO₄

• HPO₄^-

• PO₄^3-