JEE MAIN - Chemistry (2003 - No. 10)
When rain is accompanied by a thunderstorm, the collected rain water will have a pH value :
slightly higher than that when the thunderstorm is not there
uninfluenced by occurence of thunderstorm
which depends on the amount of dust in air
slightly lower than that of rain water without thunderstorm
Uitleg
The rain water after thunderstorm contains dissolved acid and therefore the $$pH$$ is less than rain water without thunderstorm.