$6.02 \times 10^{20}$ molecules of urea are present in $100 \ mL$ of its solution. The concentration of urea solution is ......... $M$.

The number of mole atoms and mole molecules in $56 \ L$ of oxygen gas at $STP$ are respectively:

$1 \text{ g}$ of $H_2$ contains the same number of molecules as in

If the market prices of table salt $(NaCl)$ and table sugar $(C_{12}H_{22}O_{11})$ are $Rs. 4$ per $kg$ and $Rs. 30$ per $kg$ respectively,then the market price of $1$ mole of each will be,respectively,..... $Rs$.

$80 \ g$ of oxygen contains as many atoms as in

Explain the mole concept.