Consider the following reactions. Na 2 B 4 O 7 xrightarrow Δ 2 X + Y CuSO 4 + Y xrightarrow Non-Luminous\; flame Z + SO 3 2 Z +2 X + Carbon xrightarrow Luminous\; flame 2 Q + Na 2 B 4 O 7 + CO The oxidation states of Cu in Z and Q , respectively are :

Chemistry · d and f Block Elements

JEE Main 2026 — 28 January, Evening Shift — Question 61

Consider the following reactions.

$\mathrm{Na}_{2} \mathrm{~B}_{4} \mathrm{O}_{7} \xrightarrow{\Delta} 2 \mathrm{X}+\mathrm{Y}$

$\mathrm{CuSO}_{4}+\mathrm{Y} \xrightarrow{\text { Non-Luminous\; flame }} \mathrm{Z}+\mathrm{SO}_{3}$

$2 \mathrm{Z}+2 \mathrm{X}+$ Carbon $\xrightarrow{\text { Luminous\; flame }} 2 \mathrm{Q}+\mathrm{Na}_{2} \mathrm{~B}_{4} \mathrm{O}_{7}+\mathrm{CO}$

The oxidation states of Cu in Z and Q , respectively are :

Option A:
$+2 and +2$
Option B:
$+2 and +1$
Correct
Option C:
$+1 and +2$
Option D:
$+1 and +1$

Answer: B

Step-by-step solution

\mathrm{Na_2B_4O_7} \;\xrightarrow{\Delta}\; 2(\mathrm{NaBO_2}) + \mathrm{B_2O_3} \quad (X)

\mathrm{CuSO_4} + \mathrm{B_2O_3} \;\xrightarrow[\text{Non-luminous\; flame}]{\Delta}\; \mathrm{Cu(BO_2)_2} + \mathrm{SO_3}

\text{(Blue\; bead)} \quad (Z)

2\,\mathrm{Cu(BO_2)_2} + 2\,\mathrm{NaBO_2} + \mathrm{C} \;\xrightarrow[\text{Luminous\; flame}]{\Delta}\; 2\,\mathrm{CuBO_2} + \mathrm{Na_2B_4O_7} + \mathrm{CO}

\text{(Colourless)} \quad (Q)

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 28 January, Evening Shift
Subject: Chemistry
Chapter: d and f Block Elements
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