CBSE 2025 · Region 4 · Set 3 · Q21 · 2 marks
The reaction between $\displaystyle \mathrm{A}_{2}(\mathrm{~g})$ and $\displaystyle \mathrm{B}_{2}(\mathrm{~g})$ was carried out in a sealed isothermal container. The rate law for the reaction was found to be : \[\text { Rate }=\mathrm{k}\left[\mathrm{~A}_{2}\right]\left[\mathrm{B}_{2}\right] \] If $\displaystyle 1$ mole of $\displaystyle \mathrm{A}_{2}(\mathrm{~g})$ was added to the reaction chamber and the temperature was kept constant, then predict the change in rate of the reaction and the rate constant.Reactant 'A' underwent a decomposition reaction. The concentration of 'A' was measured periodically and recorded in the table given below : Time/Hours [A]/M $\displaystyle 0$ $\displaystyle 0.88$ $\displaystyle 1$ $\displaystyle 0.44$ $\displaystyle 2$ $\displaystyle 0 \cdot 22$ $\displaystyle 3$ $\displaystyle 0 \cdot 11$
Based on the above data, predict the order of the reaction and write the expression for the rate law.
The reaction between $\displaystyle \mathrm{A}_{2}(\mathrm{~g})$ and $\displaystyle \mathrm{B}_{2}(\mathrm{~g})$ was carried out in a sealed isothermal container. The rate law for the reaction was found to be : \[\text { Rate }=\mathrm{k}\left[\mathrm{~A}_{2}\right]\left[\mathrm{B}_{2}\right] \] If $\displaystyle 1$ mole of $\displaystyle \mathrm{A}_{2}(\mathrm{~g})$ was added to the reaction chamber and the temperature was kept constant, then predict the change in rate of the reaction and the rate constant.
Reactant 'A' underwent a decomposition reaction. The concentration of 'A' was measured periodically and recorded in the table given below :
Based on the above data, predict the order of the reaction and write the expression for the rate law.
| Time/Hours | [A]/M |
| $\displaystyle 0$ | $\displaystyle 0.88$ |
| $\displaystyle 1$ | $\displaystyle 0.44$ |
| $\displaystyle 2$ | $\displaystyle 0 \cdot 22$ |
| $\displaystyle 3$ | $\displaystyle 0 \cdot 11$ |
Marking-scheme solution
Rate of the reaction will increase.
Rate constant remains same.
Order of the reaction =$\displaystyle 1$ / First
Rate =k[A]
Chemical KineticsFactors Influencing Rate of a ReactionUnderstandvery_short_answermedium
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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.