(a) (i) A first order reaction is 20% complete in 10 minutes. Calculate the time taken when 80% of the reaction will be completed. [Given : $\log 5 = 0\cdot7$, $\log 4 = 0\cdot6$] (ii) For a chemical reaction $\text{R} \rightarrow \text{P}$, variation in $\ln[\text{R}]$ vs. time (t) graph is given below : (I) Predict the order of the reaction. (II) Write the slope of the curve. OR (b) (i) For first order reaction, calculate the ratio between the time taken to complete $\frac{3}{4}^{\text{th}}$ of the reaction and the time taken to complete half of the reaction. (ii) (I) What is meant by a complex reaction ? (II) Give an example of a pseudo first order reaction.

Year	Paper Code	Set	Position
CBSE 2026	Series 56-7	Set 1	Question 31
CBSE 2026	Series 56-7	Set 2	Question 33
CBSE 2026	Series 56-7	Set 3	Question 32

• Step 1: Stating the fundamental formula / law statement (+1 Mark)
• Step 2: Intermediate mathematical substitution or proof steps (+1 Mark)
• Step 3: Correct final value or conclusion with mandatory SI units (+1 Mark)