Academic Experts Solutions for Chapter: d & f Block Elements, Exercise 1: Exercise

Which is a stronger reducing agent ${\mathrm{Cr}}^{2+}$ or ${\mathrm{Fe}}^{2+}$ and why?

Calculate the number of unpaired electrons in the following gaseous ions: ${\mathrm{Mn}}^{3+},{\mathrm{Cr}}^{3+},{\mathrm{V}}^{3+}$ and ${\mathrm{Ti}}^{3+}$. Which one of these is the most stable in aqueous solution?

Mercurous ion is written as ${{\mathrm{Hg}}_2}^{2+}$ whereas, cuprous ion is written as ${\mathrm{Cu}}^{+}$. Explain.

Copper sulphate dissolves in ${\mathrm{NH}}_4\mathrm{OH}$ solution but ${\mathrm{FeSO}}_4$ does not.

Among the following statements choose the true or false statement(s).

$\left(\mathrm{a}\right)$ ${\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7$ on heating with charcoal gives metallic potassium and ${\mathrm{Cr}}_2{\mathrm{O}}_3$

$\left(\mathrm{b}\right)$ On heating in current of ${\mathrm{H}}_2$, the crystalline ${\mathrm{KMnO}}_4$ is converted into $\mathrm{KOH}$ and ${\mathrm{Mn}}_3{\mathrm{O}}_4$.

$\left(\mathrm{c}\right)$ Hydrated ferric chloride on treatment with $2, 2-$dimethoxypropane gives anhydrous ferric chloride.

A compound $\left(\mathrm{A}\right)$ is used in paints instead of salts of lead. Compound $\left(\mathrm{A}\right)$ is obtained when a white compound $\left(\mathrm{B}\right)$ is strongly heated. Compound $\left(\mathrm{B}\right)$ is insoluble in water but dissolves in sodium hydroxide forming a solution of compound $\left(\mathrm{C}\right)$. The compound $\left(\mathrm{A}\right)$ on heating with coke gives a metal $\left(\mathrm{D}\right)$ and a gas $\left(\mathrm{E}\right)$ which burns with blue flame. $\left(\mathrm{B}\right)$ also dissolves in ammonium sulphate solution mixed with ammonium hydroxide. Solution of compound $\left(\mathrm{A}\right)$ in dilute $\mathrm{HCl}$ gives a bluish white / white precipitate $\left(\mathrm{F}\right)$ with excess of ${\mathrm{K}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]$. Identify $\left(\mathrm{A}\right)$ to $\left(\mathrm{F}\right)$ and explain the reactions.

An unknown inorganic compound $\left(\mathrm{X}\right)$ gave the following reactions:

(i) The compound $\left(\mathrm{X}\right)$ on heating gave a residue, oxygen and oxide of nitrogen.

(ii) An aqueous solution of compound $\left(\mathrm{X}\right)$ on addition to tap water gave a turbidity which did not dissolve in ${\mathrm{HNO}}_3$.

(iii) The turbidity dissolves in ${\mathrm{NH}}_4\mathrm{OH}$. Identify the compound $\left(\mathrm{X}\right)$ and give equations for the reactions $\left(\mathrm{i}\right), \left(\mathrm{ii}\right)$ and $\left(\mathrm{iii}\right)$.

On the basis of trends in the properties of the $3\mathrm{d}$-series elements, suggest possible ${\mathrm{M}}^{2+}$ aqua ions for use as reducing agents. Also, write a balanced chemical equation for the reaction of one of these ions with ${\mathrm{O}}_2$ in acidic solution.