IB Diploma Chemistry chapter 5: Reactivity 2: How much, how fast and how far? MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
30 exam-style questions on Reactivity 2: How much, how fast and how far?, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
R2.1 How much? The amount of chemical change11 questions
R2.2 How fast? The rate of chemical change9 questions
R2.3 How far? The extent of chemical change10 questions
Ten Reactivity 2: How much, how fast and how far? questions with answers
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. A reaction has Kc = 1 × 10−10 at 298 K. What does this tell us?
A
the equilibrium lies far to the right, so products predominate
B
the reaction is very slow at 298 K
C
the equilibrium lies far to the left, so reactants predominate
D
reactants and products are present in roughly equal amounts
Show answer
Answer: C. A very small K means the denominator (reactants) is much larger than the numerator (products) at equilibrium. K says nothing about rate.
2. According to collision theory, why do not all collisions between reactant particles lead to a reaction?
A
collisions only react if a catalyst is present
B
the colliding particles must have energy at least equal to the activation energy and a suitable orientation
C
only collisions between particles with the same kinetic energy react
D
the particles must have total energy equal to ΔH
Show answer
Answer: B. A successful collision needs enough energy to reach the transition state (E ≥ Ea) and the right geometry so the reacting atoms meet.
3. Which type of reaction always has an atom economy of 100%?
A
any reaction with a 100% percentage yield
B
an addition reaction forming a single product, such as C2H4 + H2 → C2H6
C
a substitution reaction such as CH4 + Cl2 → CH3Cl + HCl
D
a neutralization such as HCl + NaOH → NaCl + H2O
Show answer
Answer: B. When every reactant atom ends up in the one desired product, nothing is wasted. Yield and atom economy are different: a 100% yield can still make by-products.
4. What is the equilibrium constant expression for N2(g) + 3H2(g) ⇌ 2NH3(g)?
A
Kc = [NH3]2 ÷ ([N2][H2]3)
B
Kc = [N2][H2]3 ÷ [NH3]2
C
Kc = 2[NH3] ÷ ([N2] × 3[H2])
D
Kc = [NH3]2 ÷ ([N2] + [H2]3)
Show answer
Answer: A. Products over reactants, each concentration raised to the power of its coefficient and multiplied together. Coefficients are powers, not multipliers.
5. How does a catalyst increase the rate of a reaction?
A
it gives the particles more kinetic energy
B
it provides an alternative reaction pathway with a lower activation energy
C
it shifts the Maxwell–Boltzmann distribution to higher energies
D
it makes ΔH more negative
Show answer
Answer: B. With a lower Ea, a larger fraction of particles already have enough energy to react. The energy distribution and ΔH are unchanged.
6. For H2(g) + I2(g) ⇌ 2HI(g), what is the effect of increasing the total pressure at constant temperature?
A
the position shifts to the right
B
the position shifts to the left
C
the position does not change, because there are equal numbers of gas moles on each side
D
Kc increases
Show answer
Answer: C. There are 2 moles of gas on each side, so changing pressure cannot favour either direction. The rates of both reactions rise, but the position is unchanged.
7. Liquid bromine is left in a sealed flask at constant temperature. After a while the colour of the vapour stops getting darker. Which statement is correct?
A
evaporation and condensation have both stopped
B
the rate of evaporation equals the rate of condensation
C
all the liquid has evaporated
D
the rate of evaporation is greater than the rate of condensation
Show answer
Answer: B. This is a physical dynamic equilibrium: molecules still leave and return to the liquid, but at equal rates, so the vapour concentration stays constant.
8. Fe3+(aq) + SCN−(aq) ⇌ FeSCN2+(aq). Fe3+ is pale yellow and FeSCN2+ is blood-red. Solid potassium thiocyanate is added. What is observed?
A
the colour becomes paler as the equilibrium shifts to the left
B
no change, because K is constant at constant temperature
C
the red colour deepens because K increases
D
the red colour deepens as the equilibrium shifts to the right to use up the added SCN−
Show answer
Answer: D. Adding SCN− raises a reactant concentration, so the position shifts right, making more red FeSCN2+. K does not change; the concentrations adjust to restore it.
9. 25.0 g of calcium carbonate is heated: CaCO3 → CaO + CO2. What mass of calcium oxide forms? (M: CaCO3 100.09, CaO 56.08, CO2 44.01 g mol−1)
A
11.0 g
B
14.0 g
C
25.0 g
D
44.6 g
Show answer
Answer: B. n(CaCO3) = 25.0 ÷ 100.09 = 0.250 mol = n(CaO); m = 0.250 × 56.08 = 14.0 g. 11.0 g is the mass of CO2.
10. Which statement is true for a reaction at dynamic equilibrium in a closed system?
A
the concentrations of reactants and products are equal
B
the rates of the forward and reverse reactions are equal, so the concentrations stay constant
C
both reactions have stopped
D
only the forward reaction continues
Show answer
Answer: B. Both reactions continue at the same rate, so there is no overall change in concentration. The concentrations are constant but are usually not equal.
Reactivity 2: How much, how fast and how far?: questions students ask
How many Reactivity 2: How much, how fast and how far? MCQs are there?
30, each with the answer and a short explanation, across 3 topics: R2.1 How much? The amount of chemical change, R2.2 How fast? The rate of chemical change, R2.3 How far? The extent of chemical change. Every chapter test draws ten of them, so you can take it many times.
Is the IB Diploma Chemistry chapter 5 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
