The volume of oxygen required for complete combustion of $0.25 \ mol$ of methane at $S.T.P.$ is (in $dm^{3}$)

In an experiment on the enthalpy of neutralisation of sodium hydroxide with sulphuric acid,$50 \ cm^3$ of $0.4 \ M$ sodium hydroxide were titrated thermometrically with $0.25 \ M$ sulphuric acid. Which of the following plots gives the most probable correct representation of the temperature of the solution (initial temperatures of $NaOH$ and $H_2SO_4$ are the same)?

$100 \ mL$ of $0.1 \ N$ hypo solution is decolourised by the iodine liberated from the addition of $x \ g$ of crystalline copper sulphate to an excess of $KI$. The value of $x$ is ............. $g$ (molecular weight of $CuSO_4 \cdot 5H_2O$ is $250$).

What is the percentage atom economy when the formula weight of the desired product is $65 \text{ u}$ and the sum of the formula weights of all reactants is $130 \text{ u}$ (in $\%$)?

Phosphoric acid $(H_3PO_4)$ is a tribasic acid and one of its salts is sodium dihydrogen phosphate $(NaH_2PO_4)$. What volume of $1 \ M$ $NaOH$ solution should be added to $12 \ g$ of sodium dihydrogen phosphate (mol. wt. $120$) to exactly convert it into trisodium phosphate $(Na_3PO_4)$? (Answer in $mL$)

What is the volume of $O_2$ gas required at $STP$ for the combustion of $4 \ g$ of methane gas (in $L$)?