CAIE A-Level Chemistry A2 26.1.6 Effect of Temperature Change on the Rate Questions

Practise explaining qualitatively how increasing temperature raises the rate constant and hence reaction rate, relating the effect to molecular energy and successful collisions.

Exam points

state that increasing temperature increases the numerical value of the rate constant k
use the unchanged rate equation to link the larger k directly to a higher rate at fixed concentrations
avoid claiming that temperature changes the experimentally determined reaction orders

[Maximum number: 1]

Hypophosphorous acid is an inorganic acid.
The conjugate base of hypophosphorous acid is $\mathrm{H}_{2} \mathrm{PO}_{2}^{-}$ .

$\mathrm{H}_{2} \mathrm{PO}_{2}^{-}(\mathrm{aq})$ reacts with $\mathrm{OH}^{-}(\mathrm{aq})$ .

\mathrm{H}_{2} \mathrm{PO}_{2}^{-}(\mathrm{aq})+\mathrm{OH}^{-}(\mathrm{aq}) \rightarrow \mathrm{HPO}_{3}^{2-}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{~g})

Table 2.1 shows the results of a series of experiments used to investigate the rate of this reaction.

Table 2.1

Describe how an increase in temperature affects the value of the rate constant, $k_{1}$ .

( $k_{1}$ ) increases (with temperature)

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CAIE A-Level Chemistry A2 26.1.6 Effect of Temperature Change on the Rate Questions question 1