$0.05 \ cm$ thick coating of silver is deposited on a plate of $0.05 \ m^2$ area. The number of silver atoms deposited on the plate is . . . . . . $\times 10^{23}$. (Atomic mass of $Ag = 108$,density $d = 7.9 \ g \ cm^{-3}$)

What volume of $NH_3$ gas at $STP$ would be needed to prepare $100 \ mL$ of $2.5$ molal $(2.5 \ m)$ ammonium hydroxide solution? (Assume the density of the solution is $1 \ g/mL$)

Fill in the blanks given below:
$(i)$ The mass of $1$ mole of a substance expressed in grams is called its .........
$(ii)$ The amount of solute dissolved in $1$ $kg$ of solvent is called its .........
$(iii)$ The Fahrenheit scale in a thermometer is marked between .........
$(iv)$ In $NaCl$,each $Na^{+}$ ion is surrounded by ......... $Cl^{-}$ ions.

Air contains $23\% \, O_2$ and $77\% \, N_2$ by weight. What is the percentage of $O_2$ by volume?

Equal weights of $CH_{4}$ and $H_{2}$ are mixed in an empty container at $25^{\circ} C$. The fraction of the total pressure exerted by $H_{2}$ is

Mole fraction of $O_2$ in an $O_2$ and $O_3$ mixture is $0.25$. Hence,the percentage concentration $\left( \frac{w}{W}\% \right)$ of $O_2$ in the mixture is: