Embibe Experts Solutions for Chapter: Some Basic Concepts of Chemistry, Exercise 3: Level 3

The ratio of mass percent of $\mathrm{C}$ and $\mathrm{H}$ of an organic compound $\left({\mathrm{C}}_{\mathrm{X}}{\mathrm{H}}_{\mathrm{Y}}{\mathrm{O}}_{\mathrm{Z}}\right)$ is $6:1$. If one molecule of the above compound $\left({\mathrm{C}}_{\mathrm{X}}{\mathrm{H}}_{\mathrm{Y}}{\mathrm{O}}_{\mathrm{Z}}\right)$ contains half as much oxygen as required to burn one molecule of compound ${\mathrm{C}}_{\mathrm{X}}{\mathrm{H}}_{\mathrm{Y}}$ completely to ${\mathrm{CO}}_2$ and ${\mathrm{H}}_2\mathrm{O}$, what will be the empirical formula of the compound ${\mathrm{C}}_{\mathrm{X}}{\mathrm{H}}_{\mathrm{Y}}{\mathrm{O}}_{\mathrm{Z}}$? 

A mixture of $100 \mathrm{m}$ mol of $\mathrm{Ca}(\mathrm{OH}{)}_2$and $2 \mathrm{g}$of sodium sulphate was dissolved in water and the volume was made up to $100 \mathrm{mL}$. The mass of calcium sulphate formed and the concentration of ${\mathrm{OH}}^{-}$ in resulting solution are: Molar mass of $\mathrm{Ca}(\mathrm{OH}{)}_2, {\mathrm{Na}}_2{\mathrm{SO}}_4$ and ${\mathrm{CaSO}}_4$are $74,143$ and $136 \mathrm{g}$ ${\mathrm{mol}}^{-1}$ and ${\mathrm{K}}_{\mathrm{sp}}$ of $\mathrm{Ca}(\mathrm{OH}{)}_2$ is $5.5\times {10}^{-6}$ respectively.

Excess of calcium orthophosphate ${\mathrm{Ca}}_3({\mathrm{PO}}_4{)}_2$ is reacted with magnesium to form calcium phosphide $\left({\mathrm{Ca}}_3{\mathrm{P}}_2\right)$ with magnesium oxide. Calcium phosphide on reacting with an excess of water liberate phosphine gas (${\mathrm{PH}}_3$) along with calcium hydroxide. The evolved phosphine $\left({\mathrm{PH}}_3\right)$ was burnt in the air (excess of oxygen ) to yield phosphorus pentoxide $\left({\mathrm{P}}_2{\mathrm{O}}_5\right)$ along with water. How many grams of magnesium metaphosphate would be obtained, if $19.2\mathrm{g}$ of magnesium were used for reducing calcium phosphate: 

( Atomic wt. of $\mathrm{Mg}=24, \mathrm{P}=31$ )

${\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2+ 8\mathrm{Mg}⟶{\mathrm{Ca}}_3{\mathrm{P}}_2+ 8\mathrm{MgO}$
${\mathrm{Ca}}_3{\mathrm{P}}_2+{\mathrm{H}}_2\mathrm{O}⟶\mathrm{Ca}(\mathrm{OH}{)}_2+{\mathrm{PH}}_3$
${\mathrm{PH}}_3+{\mathrm{O}}_2⟶{\mathrm{P}}_2{\mathrm{O}}_5+{\mathrm{H}}_2\mathrm{O}$
$\mathrm{MgO}+{\mathrm{P}}_2{\mathrm{O}}_5⟶\mathrm{Mg}{\left({\mathrm{PO}}_3\right)}_2$

Magnesium metaphosphate

The molarity of $20\% \mathrm{w}/\mathrm{w}$ sulphuric acid of density $1.14 \mathrm{g} {\mathrm{cm}}^{-3}$ is:

$36.5\% \mathrm{w}/\mathrm{w}$ $\mathrm{HCl}$ has density equal to $1.20 \mathrm{g} {\mathrm{mL}}^{-1}$. The molarity $\left(\mathrm{M}\right)$ and molality $\left(\mathrm{m}\right)$, respectively, are:

A mixture of $2.3 \mathrm{g}$ formic acid and $4.5 \mathrm{g}$ oxalic acid is treated with conc. ${\mathrm{H}}_2{\mathrm{SO}}_4.$ The evolved gaseous mixture is passed through $\mathrm{KOH}$ pellets. Weight (in $\mathrm{g}$ ) of the remaining product at STP will be:

When a mixture of $\mathrm{NaBr}$ and $\mathrm{NaCl}$ is repeatedly digested with sulphuric acid, all the halogens are expelled and ${\mathrm{Na}}_2{\mathrm{SO}}_4$ is formed quantitatively. With a particular mixture, it was found that the weight of ${\mathrm{Na}}_2{\mathrm{SO}}_4$ obtained was precisely the same as the weight of $\mathrm{NaBr}-\mathrm{NaCl}$ mixture taken. Calculate the ratio of the weights of $\mathrm{NaCl}$ and $\mathrm{NaBr}$ in the mixture.

Give the final answer up to two places of decimal.

$0.096 \mathrm{g}$ of stannic chloride gave $25.84 \mathrm{mL}$ of its vapour at $120°\mathrm{C}$ and $350 \mathrm{mm}$ pressure. If the chloride contains $54.6\%$ of chlorine and tin has the valency equal to $4,$ what will be the atomic weight of tin?

Round-off the answer to the nearest integer.