How many moles of urea are present in $5.4 \ g$? (Molar mass $= 60 \ g/mol$)

The mass of a sample of aluminum is $54 \ g$. The mass of the same number of magnesium atoms will be ......... $g$.

The number of hydrogen atoms present in $5.4 \ g$ of urea is : (Given : Molar mass of urea: $60 \ g \ mol^{-1}$,$N_{A} = 6.022 \times 10^{23} \ particles \ mol^{-1}$)

How many moles of $BaCO_3$ will contain $1.5$ moles of oxygen atoms?

Consider two sealed jars of equal volume. One contains $2 \ g$ of hydrogen at $200 \ K$ and the other contains $28 \ g$ of nitrogen at $400 \ K$. The gases in the two jars will have

$A$ person adds $1.71 \ g$ of sugar $(C_{12}H_{22}O_{11})$ to sweeten their tea. How many carbon atoms are added? (Molar mass of sugar $= 342 \ g/mol$)