Free Reaction Kinetics MCQs with Answers
573 Reaction Kinetics MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Reaction kinetics relates reaction rate to concentration, temperature, surface area and catalysts. Questions cover rate laws, reaction order, rate constants, activation energy and the activated complex, including how a catalyst lowers the activation energy without changing the overall energy change or equilibrium position.
Last updated
573 questions · page 1 of 29
- A. concentration of a reactant or product per unit time
- B. temperature of the mixture per unit time
- C. mass of the catalyst per unit time
- D. total pressure of the system
Explanation: Rate measures how quickly reactants are consumed or products formed, so its units are usually moles per cubic decimetre per second.
Correct answer: concentration of a reactant or product per unit time- A. Raising the temperature
- B. Powdering the solid
- C. Increasing the volume of solvent without adding more solute
- D. Adding a suitable catalyst
Explanation: Adding solvent alone dilutes the solution, so the concentration of the reacting species falls and collisions become less frequent, which…
Correct answer: Increasing the volume of solvent without adding more solute- A. are of the same size
- B. collide with energy equal to or greater than the activation energy and with the correct orientation
- C. collide at low temperature
- D. collide exactly head on, regardless of energy
Explanation: Most collisions are fruitless because the molecules either rebound with too little energy to break existing bonds or meet at the wrong…
Correct answer: collide with energy equal to or greater than the activation energy and with the correct orientation- A. the activation energy of the reaction falls
- B. the concentration of the reactants increases
- C. the molecules become larger
- D. a much larger fraction of molecules acquire energy equal to or above the activation energy
Explanation: The Maxwell Boltzmann distribution shifts to the right on heating, and because the activation energy lies out in the tail of the curve…
Correct answer: a much larger fraction of molecules acquire energy equal to or above the activation energy- A. increasing the kinetic energy of the reacting molecules
- B. raising the temperature of the reaction mixture
- C. providing an alternative pathway with a lower activation energy
- D. increasing the concentration of the reactants
Explanation: By offering a route with a smaller energy barrier, a catalyst allows a far larger proportion of collisions to be effective at the same…
Correct answer: providing an alternative pathway with a lower activation energy- A. is always equal to its coefficient in the balanced equation
- B. is the power to which its concentration is raised in the experimentally determined rate equation
- C. can never be zero
- D. is always a whole number
Explanation: Order is an experimental quantity and must be measured, because the balanced equation describes the overall stoichiometry while the rate…
Correct answer: is the power to which its concentration is raised in the experimentally determined rate equation- A. 1
- B. 2
- C. 3
- D. 4
Explanation: Overall order is the sum of the individual orders, so 1 for A plus 2 for B gives 3.
Correct answer: 3- A. doubles when the concentration doubles
- B. is independent of the concentration of the reactant
- C. falls to zero immediately
- D. is proportional to the square of the concentration
Explanation: A zero order reaction proceeds at a constant rate until the reactant is nearly exhausted, because something other than concentration…
Correct answer: is independent of the concentration of the reactant- A. melt the reactants
- B. break all the bonds in the products
- C. form the activated complex from the reactants
- D. keep the products stable
Explanation: Reactant molecules must climb an energy barrier to reach the transient, unstable arrangement called the activated complex or transition…
Correct answer: form the activated complex from the reactants- A. a stable intermediate that can be isolated
- B. the same as the catalyst
- C. the product of the reaction
- D. a short lived arrangement at the top of the energy barrier in which bonds are partly broken and partly formed
Explanation: At the transition state old bonds are stretched and new ones are only beginning to form, so the species exists for the duration of a…
Correct answer: a short lived arrangement at the top of the energy barrier in which bonds are partly broken and partly formed- A. the products lie at a lower energy level than the reactants
- B. the products lie above the reactants
- C. there is no activation energy barrier
- D. the activation energy is always zero
Explanation: An exothermic reaction releases energy to the surroundings, so the products sit lower and the enthalpy change is negative, but the curve…
Correct answer: the products lie at a lower energy level than the reactants- A. mol dm-3 s-1
- B. s-1
- C. mol-1 dm3 s-1
- D. mol-2 dm6 s-1
Explanation: For a first order reaction rate equals k times concentration, so k must have units of rate divided by concentration, which reduces to…
Correct answer: s-1- A. the concentration of the reactants is increased
- B. the volume of the vessel is changed
- C. the temperature is changed
- D. more product is removed
Explanation: The rate constant is constant only at a fixed temperature; the Arrhenius equation shows it rising sharply as temperature increases or as…
Correct answer: the temperature is changed- A. doubles as the reaction proceeds
- B. depends on the initial concentration
- C. is constant and independent of the initial concentration
- D. is always one second
Explanation: For first order kinetics the time taken for the concentration to fall by half is fixed, so successive halvings take equal times, and this…
Correct answer: is constant and independent of the initial concentration- A. concentration of the solid
- B. temperature of the mixture
- C. activation energy
- D. surface area available for collisions
Explanation: A reaction between a solid and a fluid can only occur at the exposed surface, so grinding the solid exposes far more particles and the…
Correct answer: surface area available for collisions- A. the fastest step
- B. the slowest step, which controls the overall rate
- C. always the first step
- D. the step with the largest number of molecules
Explanation: An overall reaction can proceed no faster than its slowest stage, in the same way that a road is only as clear as its narrowest point, so…
Correct answer: the slowest step, which controls the overall rate17. In the reaction between marble chips and hydrochloric acid, the rate can be followed by measuring
- A. the mass of the flask, which falls as carbon dioxide escapes
- B. the colour of the acid
- C. the temperature of the marble
- D. the mass of the flask, which rises as gas is produced
Explanation: Carbon dioxide leaves the open flask, so the total mass decreases steadily and the loss per unit time is a direct measure of the rate.
Correct answer: the mass of the flask, which falls as carbon dioxide escapes- A. It remains chemically unchanged at the end of the reaction
- B. It is needed only in a small amount
- C. It shifts the equilibrium towards the products
- D. It lowers the activation energy of both the forward and reverse reactions
Explanation: Because a catalyst lowers the barrier equally in both directions, the two rates rise by the same factor and the equilibrium position and…
Correct answer: It shifts the equilibrium towards the products- A. first order in A
- B. second order in A
- C. third order in A
- D. zero order in A
Explanation: If concentration has no effect on rate then the exponent of that term must be zero, since anything raised to the power zero equals one.
Correct answer: zero order in A- A. the activation energy increases
- B. the temperature falls
- C. the activation energy decreases or the temperature rises
- D. the concentration of reactants rises
Explanation: The equation contains an exponential term in which activation energy appears with a negative sign and temperature in the denominator, so…
Correct answer: the activation energy decreases or the temperature risesReaction Kinetics MCQs: common questions
Are these Reaction Kinetics MCQs free?
Yes. All Reaction Kinetics MCQs from Chemistry are free on TestUstad, with unlimited attempts and no account needed. Nothing on this page is a sample or a trial.
How many Reaction Kinetics MCQs are on this page?
There are 573 Reaction Kinetics MCQs in the Chemistry bank, shown 20 to a page with the correct answer and an explanation on each.
Does every Reaction Kinetics MCQ have an explanation?
Yes. Each Reaction Kinetics question shows the correct option and a written explanation of why it is correct, so a wrong answer teaches you something rather than just being marked wrong.
Can I take a timed Reaction Kinetics test?
Yes. The practice button on this page starts a free Reaction Kinetics test drawn from the Chemistry bank. It marks each answer instantly, gives you a score at the end, and can be retaken as many times as you like.