Question

The green colour produced in the borax bead test of a chromium (III) salt is due to

A. $$C{r_2}{\left( {{B_4}{O_7}} \right)_3}$$
B. $$C{r_2}{O_3}$$
C. $$Cr{\left( {B{O_2}} \right)_3}$$  
D. $$CrB$$
Answer :   $$Cr{\left( {B{O_2}} \right)_3}$$
Solution :
\[N{{a}_{2}}{{B}_{4}}{{O}_{7}}.10{{H}_{2}}O\xrightarrow{\Delta }N{{a}_{2}}{{B}_{4}}{{O}_{7}}\]       \[\xrightarrow{\Delta }2NaB{{O}_{2}}+{{B}_{2}}{{O}_{3}}\]
\[C{{r}_{2}}{{O}_{3}}+3{{B}_{2}}{{O}_{3}}\to \underset{\begin{smallmatrix} \text{Chromium meta borate} \\ \text{(green colour) } \end{smallmatrix}}{\mathop{2Cr{{\left( B{{O}_{2}} \right)}_{3}}}}\,\]

Releted MCQ Question on
Inorganic Chemistry >> Qualitative Analysis

Releted Question 1

The ion that cannot be precipitated by both $$HCl\,{\text{and}}\,{H_2}S$$    is

A. $$P{b^{2 + }}$$
B. $$C{u^ + }$$
C. $$A{g^ + }$$
D. $$S{n^{2 + }}$$
Releted Question 2

Which one among the following pairs of ions cannot be separated by $${H_2}S$$  in dilute hydrochloric acid?

A. $$B{i^{3 + }},S{n^{4 + }}$$
B. $$A{l^{3 + }},H{g^{2 + }}$$
C. $$Z{n^{2 + }},C{u^{2 + }}$$
D. $$N{i^{2 + }},C{u^{2 + }}$$
Releted Question 3

An aqueous solution contains $$H{g^{2 + }},Hg_2^{2 + },P{b^{2 + }}\,{\text{and}}\,C{d^{2 + }}.$$
The addition of $$HCl\left( {6N} \right)$$   will precipitate:

A. $$H{g_2}C{l_2}\,{\text{only}}$$
B. $$PbC{l_2}\,{\text{only}}$$
C. $$PbC{l_2}\,{\text{and}}\,H{g_2}C{l_2}$$
D. $$PbC{l_2}\,{\text{and}}\,HgC{l_2}$$
Releted Question 4

Identify the correct order of solubility of $$N{a_2}S,\,CuS\,{\text{and}}\,ZnS$$     in aqueous medium

A. $$CuS > ZnS > N{a_2}S$$
B. $$ZnS > N{a_2}S > CuS$$
C. $$N{a_2}S > CuS > ZnS$$
D. $$N{a_2}S > ZnS > CuS$$

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