Example $4$

A student collecting $245mL$ of oxygen gas by the method illustrated in Figure $9\mathrm{.}15$ records the atmospheric pressure as $99\mathrm{.}2$kPa and the temperature in the laboratory as $24C.$ Given that the vapour pressure of water is $3\mathrm{.}0$kPa at $24C,$ what mass of oxygen has been collected?

$]=nRT[\frac{PV}{RT}$

In this question they use water vapour are we expected to always subtract water vapour in every question we do even if they dont tell you the amount of water vapour?when are we supposed to subtract water vapour? In the question below should we subtract water vapour?

Oxygen gas is produced by the process of photosynthesis:

$6H_{2}O(l)+6C{O}_2(aq)C_6{H}_{12}{O}_6(aq)+6O_2(g)$

If a plant absorbs $0\mathrm{.}12g$ of carbon dioxide, what volume of oxygen gas $($in $mL)$ is produced at $15C$ and $102$kPa pressure?