Embibe Experts Solutions for Chapter: Some Basic Concepts of Chemistry, Exercise 2: EXERCISE-2

How many grams of urea on heating yield ${10}^{22}$ molecules of biuret by the reaction: $2\mathrm{CO}{\left({\mathrm{NH}}_2\right)}_2⟶{\mathrm{H}}_2 \mathrm{N}-\mathrm{CO}-\mathrm{NH}-\mathrm{CO}-{\mathrm{NH}}_2+{\mathrm{NH}}_3?$

$1 \mathrm{mol}$ of iron $\left(\mathrm{Fe}\right)$ reacts completely with $0.65 {\mathrm{molO}}_2$ to give a mixture of only $\mathrm{FeO}$ and ${\mathrm{Fe}}_2{\mathrm{O}}_3.$ Mole ratio of ferrous oxide to ferric oxide is :-

The molar ratio of ${\mathrm{Fe}}^{++}$ to ${\mathrm{Fe}}^{+++}$ in a mixture of ${\mathrm{FeSO}}_4$ and ${\mathrm{Fe}}_2{\left({\mathrm{SO}}_4\right)}_3$ having equal number of sulphate ion in both ferrous and ferric sulphate is :-

An ore of iron, Wustite has the formula ${\mathrm{F}}_{0.93}{\mathrm{O}}_{1.00}.$ The mole fraction of total iron present in the form of $\mathrm{Fe}\left(\mathrm{II}\right)$ is :-

$28{\mathrm{NO}}_3^{-}+3{\mathrm{As}}_2{ \mathrm{S}}_3+4{\mathrm{H}}_2\mathrm{O}\to 6{\mathrm{AsO}}_4{}^{3-}+28\mathrm{NO}+9{\mathrm{SO}}_4{}^{2-}+{\mathrm{H}}^{+}$

What will be the equivalent mass of ${\mathrm{As}}_2{\mathrm{S}}_3$ in above reaction

An element forms two different sulphates in which its weight $\%$ is $28$ and $37.$ What is the ratio of oxidation numbers of the element in these sulphates?

$4.9 \mathrm{gm}$ of ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ is taken to prepare $0.1 \mathrm{L}$ of the solution. $10 \mathrm{mL}$ of this solution is further taken to oxidise ${\mathrm{Sn}}^{2+}$ ion into ${\mathrm{Sn}}^{4+}$ ion ${\mathrm{Sn}}^{4+}$ so produced is used in $2^{\text{nd }}$ reaction to prepare ${\mathrm{Fe}}^{3+}$ ion then the millimoles of ${\mathrm{Fe}}^{3+}$ ion formed will be (assume all other components are in sufficient amount) [Molar mass of ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7=294 \mathrm{g}$ ].

$0.10 \mathrm{g}$ of a sample containing ${\mathrm{CuCO}}_3$ and some inert impurity was dissolved in dilute sulphuric acid and volume made up to $50 \mathrm{mL}.$ This solution was added into $50 \mathrm{mL}$ of $0.04 \mathrm{MKI}$ solution where copper precipitates as $\mathrm{CuI}$ and ${\mathrm{I}}^{-}$is oxidized into ${\mathrm{I}}_3^{-}.$ A $10 \mathrm{mL}$ portion of this solution is taken for analysis, filtered and made up free ${\mathrm{I}}_3^{-}$ and then treated with excess of acidic permanganate solution. Liberated iodine required $20 \mathrm{mL}$ of $2.5 \mathrm{mM}$ sodium thiosulphate solution to reach the end point.

Determine weight percentage of ${\mathrm{CuCO}}_3$ in the original sample,