An oxide of copper which is red in colour has the formula

An organic compound with $C = 40\%$ and $H = 6.7\%$ will have the empirical formula

$0.48 \ g$ of an organic compound on complete combustion produced $0.22 \ g$ of $CO_2$. The percentage of $C$ in the given organic compound is

The percentage of $N_2$ in urea is about

An organic compound weighing $500 \ mg$ produced $220 \ mg$ of $CO_2$ on complete combustion. The percentage composition of carbon in the compound is $..........\%$. $(nearest \ integer)$ $(Given \ molar \ mass \ in \ g \ mol^{-1} \ of \ C: 12, O: 16)$

The empirical formula of a hydrocarbon containing $80\%$ carbon and $20\%$ hydrogen is: