JEE Advanced levelOne or more correct optionsDifficulty 3 of 3ck110
The gas-phase decomposition of A shows a half-life of 100s when the initial pressure is 300mmHg and again 100s when it is 150mmHg. Take log2=0.3010 and ln2=0.693. Select the correct statement(s).
AThe reaction is first order.
BThe time for 75% decomposition is 300s.
CThe rate constant is 6.93×10−3s−1.
DThe time for 90% decomposition is 332s.
Answer: A, C, D
A half-life independent of the initial pressure indicates first order, with k=0.693/100=6.93×10−3s−1. For 75% decomposition two half-lives are needed, 200 s (not 300 s). For 90%, t=(2.303/k)log10=100/0.3010=332s.