Nickel steel contains $3-5 \%$ of $Ni$. (in $-5 \%$)

Reduction of $7.2 \, g$ of a metal oxide yields $6.4 \, g$ of the metal. If the atomic mass of the metal is $128 \, g/mol$,the formula of the oxide is .....

$A$ gas is found to have a formula $[CO]_x$. If its vapour density is $70$,the value of $x$ is

An organic compound has an empirical formula of $CH_2O$ and a molecular mass of $90$. What is its molecular formula? $(C = 12, H = 1, O = 16)$

$A$ sample of calcium carbonate $(CaCO_3)$ has the following percentage composition: $Ca = 40\%$; $C = 12\%$; $O = 48\%$. If the law of constant proportions is true,then the weight of calcium in $4 \, g$ of a sample of calcium carbonate obtained from another source will be $... \, g$.

If two compounds have the same empirical formula but different molecular formulas,which of the following do they possess?