NEET Chemistry: Chemistry - Kinetics questions with solutions

Q1. \( 80 \% \) of a first order reaction was completed in 70 min. How much it will take for \( 90 \% \) completion of a reaction?

1. 114 min
2. 140 min
3. \( 100 \mathrm{min} \)
4. 200 min

Answer: 114 min

For a first-order reaction, time depends on the logarithm of the fraction remaining. Since 80% completion means 20% remains after 70 min, you can determine the rate constant and then calculate the time for 10% remaining. This gives about 114 min.