The decomposition of a compound is found to follow a first order rate law. If it takes 15 minutes for 20% of the original material to react, calculate:
i) the specific rate constant,
ii) the time at which 10% of the original material remains unreacted,
iii) the time it takes for the next 20% of the reactant left to react after the first 15 minutes.
i) the specific rate constant,
ii) the time at which 10% of the original material remains unreacted,
iii) the time it takes for the next 20% of the reactant left to react after the first 15 minutes.
Answer: (i) k ≈ 0.0149 min⁻¹ (ii) ≈ 155 min (iii) 15 min (same fractional change → same time).
Solution
(i)
(ii) 10% remaining means :
(iii) 'Next 20% of the reactant left': from 80% down to :
In a first order reaction an equal fractional change always takes the same time —
(ii) 10% remaining means :
(iii) 'Next 20% of the reactant left': from 80% down to :
In a first order reaction an equal fractional change always takes the same time —
CBSE Class 12 Board · 2002 · Delhi · Subjective