The density of trifluoroacetic acid vapour was determined at $117 °\mathrm{C}$ and $470 \mathrm{mm} \mathrm{Hg}$ and was found to be $2.784 \mathrm{g}/\mathrm{L}$. Calculate ${\mathrm{K}}_{\mathrm{c}}$ for:

If the reaction between steam and iron proceeds as

$3 \mathrm{Fe} \left(\mathrm{s}\right)+4{\mathrm{H}}_2\mathrm{O} \left(\mathrm{g}\right)\rightleftharpoons {\mathrm{Fe}}_3{\mathrm{O}}_4 \left(\mathrm{s}\right)+4{\mathrm{H}}_2 \left(\mathrm{g}\right)$

and partial pressures of steam and hydrogen are $50 \mathrm{mm}$ and $940 \mathrm{mm}$, respectively at $250°\mathrm{C}$. Calculate the partial pressure of steam at equilibrium when partial pressure of hydrogen is $1800 \mathrm{mm}$.

Answer correct up to one place of decimal.

A chemist needs a buffer with $\mathrm{pH}$ $4.35.$ How many $\mathrm{mL}$ of pure acetic acid (density $=1.049 \mathrm{g}/\mathrm{mL}$ ) must be added to $465 \mathrm{mL}$ of  $0.0941 \mathrm{M} \mathrm{NaOH}$ solution to obtain such a buffer? $\left(\mathrm{pKa} {\mathrm{CH}}_3\mathrm{COOH} = 4.74\right)$

Give answer after multiplying with 10 and rounding off to the nearest integer value.

A quantity of $0.25 \mathrm{M} \mathrm{NaOH}$ is added to a solution containing $0.15$mole of acetic acid. The final volume of the solution is $375 \mathrm{mL}$ and the $\mathrm{pH}$ of the solution is $4.45$. $\left({\mathrm{pK}}_{\mathrm{a}} {\mathrm{CH}}_3\mathrm{COOH} = 4.47, {10}^{-0.02}=0.948\right)$

What was the original concentration of the acetic acid?

Round off your to the nearest integer.

The reaction:

${\mathrm{Sb}}_2{\mathrm{S}}_3\left(\mathrm{s}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\rightleftharpoons 2\mathrm{Sb}\left(\mathrm{s}\right)+3{\mathrm{H}}_2\mathrm{S}\left(\mathrm{g}\right)$

was studied by analysing the equilibrium mixture for the amount of ${\mathrm{H}}_2\mathrm{S}$ produced. A vessel whose volume was $\text{2.5 litre}$ was filled with $0.01$mole of ${\mathrm{Sb}}_2{\mathrm{S}}_3$ and$0.01$ mole of ${\mathrm{H}}_2$. After the mixture came to equilibrium in the closed vessel at $440°\mathrm{C},$ the gaseous mixture was removed, and the ${\mathrm{H}}_2\mathrm{S}$ was dissolved in water. Sufficient ${\mathrm{Pb}}^{2+}$ ions were added to react completely with the ${\mathrm{H}}_2\mathrm{S}$ to precipitate $\mathrm{PbS}$ . If $1.029 \mathrm{g}$ of $\mathrm{PbS}$ was obtained, what is the value of ${\mathrm{K}}_{\mathrm{c}}$ at $440°\mathrm{C}?$

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

The following equilibrium exists in a closed system at $25°\mathrm{C}$ ${\mathrm{NH}}_4\mathrm{HS} \left(\mathrm{s}\right)\rightleftharpoons {\mathrm{NH}}_3 \left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{S} \left(\mathrm{g}\right)$.

When a sample of pure ${\mathrm{NH}}_4\mathrm{HS} \left(\mathrm{s}\right)$ is placed in an evacuated vessel and allowed to reach equilibrium at $25°\mathrm{C}$, the total pressure is $0.66 \mathrm{atm}$. Find the value of ${\mathrm{K}}_{\mathrm{p}}$. (Give answer after multiplying with 100 and rounding off to the nearest integer value.)