Let's say I have a container with fixed volume, containing Hydrogen Gas at some predefined temperature. Now I pass an electric spark in the whole container such that this reaction takes place
$$H_2 \rightarrow 2H$$
Now actually the number of moles of Hydrogen(atoms) remain constant, the volume is also constant, would there be an increase in pressure assuming the whole situation to be ideal. I just want to know the contribution in increment due to dissociation and not due to increase in temperature of the gas due to the electric spark. Will the pressure increase, decrease or remain constant?