Question

A solution of A is mixed with an equal volume of solution of B containing the same no. of moles & following reaction occurs A + B ¾® C. At the end of 1 hr, A is 75% reacted. How much of A will be left unreacted at the end of 2 hr if the reaction is 1^st order in A & zero order in B –

• A. 0%
• B. 12.5%
• C. 6.25%
• D. 25%

Answer 1

Answer: (C)

6.25%

Answer 2

w.r.t A reaction follows 1^st order i.e. half life is constant.

Remaining A after 2 half life i.e. 1 hr = 25%

Remaining A after 3 half life i.e.$1\frac{1}{2}$hr = 12.5 %

Remaining A after 4 half life i.e. 2 hr = 6.25%