Which of the following are correct statements about eudiometry (gas analysis in a graduated tube over mercury)?

AVolumes of gases measured at the same $T$ and $P$ are proportional to their moles
BWater formed is neglected in the volume of residual gas when measurements are made at room temperature
CThe volume of $CO X_{2}$ formed is found from the contraction on adding KOH
DNitrogen formed from combustion of a nitrogen compound is absorbed by KOH

Answer: A, B, C

Avogadro's law makes volume ratios equal to mole ratios (A). Water is liquid at room temperature and occupies negligible volume (B). KOH absorbs

CO X_{2}

and the decrease in volume gives its amount (C).

N X_{2}

is not absorbed by KOH; it stays in the residual gas (D wrong).