When $3.06 \mathrm{g}$ of solid ${\mathrm{NH}}_4\mathrm{HS}$ is introduced into a two-litre evacuated flask at $27° \mathrm{C}$. $30\%$ of the solid decomposes into gaseous ${\mathrm{NH}}_3$ and ${\mathrm{H}}_2\mathrm{S}$.

What would happen to the equilibrium when more solid ${\mathrm{NH}}_4\mathrm{HS}$ is introduced into the flask?

The pressure exerted by $12 \mathrm{g}$ of an ideal gas at temperature $\mathrm{t}° \mathrm{C}$ in a vessel of volume $\mathrm{V}$ $\mathrm{litre}$ is one $\mathrm{atm}$. When the temperature is increased by $10 \mathrm{degrees}$at the same volume, the pressure increases by $10\%$. Calculate the temperature $\mathrm{t}$ and volume $\mathrm{V}$. (Molecular weight of the gas $=120$)

The solubility of $\mathrm{Pb}(\mathrm{OH}{)}_2$ in water is $6.7\times {10}^{-6} \mathrm{M}$. Calculate the solubility of $\mathrm{Pb}(\mathrm{OH}{)}_2$ in a buffer solution of $\mathrm{pH}=8$.

If the answer is of type $\mathrm{y}\times {10}^{-3} \mathrm{M}$, report the value of $\mathrm{y}$ correct up to one decimal place.

The rate constant for an isomerisation reaction $\mathrm{A}\to \mathrm{B}$ is $4.5\times {10}^{-3} {\min }^{-1}$ . If the initial concentration of $\mathrm{A}$ is $1 \mathrm{M}$, calculate the rate after $1 \mathrm{hr}.$

If the answer is of type $\mathrm{y}\times {10}^{-3} \mathrm{M} {\min }^{-1}$, report the value of $\mathrm{y}$ correct up to one decimal place.

A metal cystallises into two cubic phases, f.c.c and b.c.c. whose unit-cell lengths are $3.5 {\mathrm{A}}^{°}$ and $3.0 \mathrm{A}°$. Calculate the ratio of densities of f.c.c. and b.c.c.

Give answer after multiplying with 100 and rounding off to the nearest integer value.