The half-life time for a 1st order decomposition of a substance dissolved in CCL4 is 2.5 hours at 30°C. The amount of substance left after 10 hours if the initial weight of the substance is 160g
Correct answer: B. 10g
- A. 5g
- B. 10g
- C. 15g
- D. 20g
Explanation
To determine the amount of substance remaining after 10 hours, calculate the number of half-lives that have passed. Since the half-life is 2.5 hours, 10 hours corresponds to 4 half-lives (10 hours ÷ 2.5 hours/half-life = 4 half-lives). Starting with 160g, the amount remaining is (1/2)4 × 160g = 10g. Option B is correct. The other options incorrectly calculate the remaining amount after 4 half-lives.
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