In a solution of $7.8 \ g$ benzene $(C_6H_6)$ and $46.0 \ g$ toluene $(C_6H_5CH_3)$,the mole fraction of benzene in this solution is:

$36 \ g$ of water and $828 \ g$ of ethyl alcohol form an ideal solution. The mole fraction of water in it is:

The molarity of the solution prepared by dissolving $6.3 \ g$ of oxalic acid $(H_{2}C_{2}O_{4} \cdot 2H_{2}O)$ in $250 \ mL$ of water in $mol \ L^{-1}$ is $x \times 10^{-2}$. The value of $x$ is ..... . (Nearest integer)
[Atomic mass : $H: 1.0, C: 12.0, O: 16.0]$

The molality of an aqueous solution of glucose is $1.0 \ m$. The mole fraction of glucose is approximately ........

$A$ solution contains $25\%$ ${H_2}O$,$25\%$ ${C_2}{H_5}OH$ and $50\%$ ${CH_3}COOH$ by mass. The mole fraction of ${H_2}O$ would be

$50 \ g$ of a substance is dissolved in $1 \ kg$ of water at $90^{\circ} C$. The temperature is reduced to $10^{\circ} C$. The density is increased from $1.1 \ g \ cm^{-3}$ to $1.15 \ g \ cm^{-3}$. What is the $\%$ change of molarity of the solution?