JEE Main · 2026 · 05 Apr 2026 · Shift 1 · Chemical Kinetics

If the half life of a first order reaction is 6.93 minutes then the time required for completion of

99%

of the reaction will be

____

minutes.
(Given :

lo g 2 = 0.3010

)

Answer: 46

Solution

For a first-order reaction the rate constant follows from the half-life as

k = \frac{ln 2}{t _{1/2}} = \frac{0.693}{6.93} = 0.1 mi n^{- 1}

. Completion of

99%

leaves one hundredth of the reactant, so

t = \frac{2.303}{k} lo g \frac{100}{1} = \frac{2.303}{0.1} \times 2 = 46.06 min

. The time required for

99%

completion is

46

minutes.

JEE Main · 2026 · 05 Apr 2026 · Shift 1 · Integer answer