CBSE 2025 · Region 7 · Set 1 · Q24 · 3 marks

The following data were obtained during the first order thermal decomposition of $\displaystyle \mathrm{N}_{2} \mathrm{O}_{5}(\mathrm{~g})$ at constant volume : \[2 \mathrm{~N}_{2} \mathrm{O}_{5}(\mathrm{~g}) \longrightarrow 2 \mathrm{~N}_{2} \mathrm{O}_{4}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \]

S.No.	Time/s	Total Pressure/atm
$\displaystyle 1$	$\displaystyle 0$	$\displaystyle 0.5$
$\displaystyle 2$	$\displaystyle 100$	$\displaystyle 0.625$

Calculate rate constant. [ Given : $\displaystyle \log 2=0 \cdot 3010, \log 10=1$ ]

CBSE Class 12 Chemistry past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.