Equal masses of methane and oxygen are mixed in an empty container at $25^\circ C$. The fraction of the total pressure exerted by oxygen is

$0.63 \ g$ of oxalic acid is dissolved to obtain $250 \ cm^3$ of its solution. Find the normality of this solution. [Oxalic acid: $(COOH)_2 \cdot 2H_2O$] (in $N$)

Sodium oxide reacts with water to produce sodium hydroxide. $20.0 \ g$ of sodium oxide is dissolved in $500 \ mL$ of water. Neglecting the change in volume,the concentration of the resulting $NaOH$ solution is $........ \times 10^{-1} \ M.$ (Nearest integer)
[Atomic mass $: Na=23.0, O=16.0, H=1.0]$

As per the following equation, $0.217 \ g$ of $HgO$ (molecular mass $= 217 \ g \ mol^{-1}$) reacts with excess iodide. On titration of the resulting solution, how many $mL$ of $0.01 \ M$ $HCl$ is required to reach the equivalence point (in $mL$)?
$HgO + 4 I^{-} + H_2O \longrightarrow HgI_4^{2-} + 2 OH^{-}$

The chloride of a metal has the formula $MCl_3$. The formula of its phosphate will be

One and a half mole of oxygen combine with aluminium to form $Al_2O_3$. The weight of aluminium metal used in this reaction is .............. $g$ (Atomic weight of $Al = 27$).