Free Rate Constant MCQs with Answers
16 Rate Constant MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
The rate constant, k, connects reaction rate with reactant concentrations in a rate law and has a value fixed for a particular reaction at a given temperature. Questions involve determining k from rate data, identifying its units for different reaction orders, and applying the Arrhenius equation to temperature changes.
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16 questions
- 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. 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 rises- A. Rate law
- B. Rate constant
- C. Reaction rate
- D. Reaction order
Explanation: The rate law, or rate equation, states the rate as the rate constant multiplied by concentration terms raised to their experimentally…
Correct answer: Rate law- A. All electrolytes
- B. Strong electrolytes
- C. Non electrolytes
- D. Weak electrolytes
Explanation: Ostwald's dilution law relates the degree of ionisation of a weak electrolyte to its concentration and is derived using its equilibrium…
Correct answer: Weak electrolytes- A. Arrhenius constant
- B. Molecularity
- C. Specific rate constant
- D. Ideal rate constant
Explanation: The specific rate constant, or rate constant k, is the reaction rate when the molar concentrations of all reactants in the rate expression…
Correct answer: Specific rate constant- A. I and II quadrant
- B. II and III quadrant
- C. III and IV quadrant
- D. II and IV quadrant
Explanation: The Arrhenius equation in logarithmic form is log k = log A - Ea/(2.303R) x 1/T, so a plot of log k against 1/T has a negative slope.
Correct answer: II and IV quadrant- A. Time
- B. Concentration of the reactant
- C. Temperature
- D. Concentration of the product
Explanation: For a given reaction, the first-order rate constant remains independent of reactant concentration and changes mainly with temperature…
Correct answer: Temperature- A. s-1
- B. mol dm-3 s-1
- C. mol-1 dm3 s-1
- D. mol-2 dm6 s-1
Explanation: For a zero-order reaction, rate = k, so k has the same dimensions as rate: concentration per time. Therefore its unit is mol dm^-3 s^-1.
Correct answer: mol dm-3 s-1- A. First order reaction
- B. Second order reaction
- C. Zero order reaction
- D. Third order reaction
Explanation: For a zero-order reaction, rate = k, so the numerical value and units of k are the same as those of the reaction rate, commonly mol dm-3…
Correct answer: Zero order reaction- A. conc.s-1
- B. M2s-1
- C. s-1
- D. M-1s-1
- E. M-1s-2
Explanation: The unit of the rate constant for a first-order reaction is s-1. This is because, for a first-order reaction, the rate is directly…
Correct answer: s-1- A. First order reaction
- B. Zero order reaction
- C. Second order reaction
- D. Third order reaction
Explanation: Rate law general form:Rate = k[A]n n = order of reactionk = rate constantUnit of k depends on the order:k = Rate[A]n
Correct answer: Zero order reaction- A. Has fixed value at fixed temperature
- B. Changes with change in temperature
- C. Does not depend upon concentration of reactants
- D. None of the above
Explanation: The explanation for this question will be added soon.
Correct answer: None of the above- A. Unit rate constant
- B. Specific rate constant
- C. Relative rate constant
- D. Average rate constant
Explanation: A specific rate constant at a given temperature may be defined as the rate of reaction when the molar concentration of each reactant is…
Correct answer: Specific rate constant- A. Sec
- B. Sec-¹
- C. Mol dm-³sec-¹
- D. None of the above
Explanation: Because the units of the reaction rate are always moles per liter per second, the units of a first-order rate constant are reciprocal…
Correct answer: Sec-¹Rate Constant MCQs: common questions
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There are 16 Rate Constant MCQs in the Chemistry bank, shown 20 to a page with the correct answer and an explanation on each.
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Yes. Each Rate Constant 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.
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