Find the mass of potassium chlorate required to liberate $5.6 \ dm^3$ of oxygen gas at $STP$. (Molar mass of $KClO_3 = 122.5 \ g/mol$) (in $g$)

To a $25 \, mL$ of $H_2O_2$ solution,an excess of acidified solution of $KI$ was mixed. The liberated $I_2$ required $20 \, mL$ of $0.3 \, M$ hypo $(Na_2S_2O_3)$ solution for neutralization. The volume strength of $H_2O_2$ is......$mL$.

How many grams of dibasic acid (mol. wt. $200$) should be present in $100 \ mL$ of its aqueous solution to give decinormal strength?

The molecular weight of a gas is $45$. Its density at $STP$ is

Change in volume when $10 \, mL$ of phosphine $(PH_3)$ is decomposed according to the reaction: $2PH_{3(g)} \rightarrow 2P_{(s)} + 3H_{2(g)}$.

The amount of carbon dioxide evolved upon complete combustion of $116 \ g$ of $n$-butane is
(Given : atomic mass in amu $H = 1, C = 12$ and $O = 16$) (in $g$)