Which one of the following represents correctly the units of the rate constant k for a first order reaction?
Correct answer: A. s-1
- A. s-1
- B. mol.dm-3s-1
- C. mol dm-1s
- D. mol-1dm1s
Explanation
rate has units of, for example, mol dm^-3 s^-1 (concentration per unit time).k (rate constant) needs to have units that cancel out the units of [A] to give the correct units for rate.[A] (concentration of reactant A) has units of mol dm^-3 (moles per unit volume).In order to find the units of k : rate/ [A] = mol dm^-3 s^-1 / mol dm^-3 = s^-1 .Option A represents the correct unit for the rate constant for a first-order reaction. It implies that the rate constant is measured in inverse seconds (per second), which cancels out the units of concentration.
Last updated
About Reaction Kinetics
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.
Practise Reaction Kinetics
573 free Reaction Kinetics MCQs from Chemistry, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Chemistry questions like this
Chemistry is on 12 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
Related questions
100 g of a substance decays slower than 50 g of the same substance. The order of decay follows kinetics:
12.Rate of disappearance of reactant is equal to
13.Rate of reaction, when concentration of reactants are taken as unity is called
14.Order of reaction of N2O5→2N2O5+ O2
16.Which order of reaction obeys the relation t1/2= 1/Ka