$138 \ g$ of ethyl alcohol is mixed with $72 \ g$ of water. The ratio of mole fraction of alcohol to water is

If a gaseous mixture contains $20\%$ $H_2$ by weight,what is the number of moles of $H_2$ in $100 \ g$ of the mixture (in $mol$)?

The density of water is $1 \, g/mL$. What is the volume occupied by $1$ molecule of water :-

Which of the following substances consists of a total of $1 \ mol$ of atoms? (Molar mass of $NH_3 = 17 \ g/mol, H_2O = 18 \ g/mol, N_2 = 28 \ g/mol, CO_2 = 44 \ g/mol$)

Which one of the following has the maximum number of atoms of oxygen?

$6.02 \times 10^{20}$ molecules of urea are present in $200 \ mL$ of its solution. The concentration of urea solution is .............. $M$