Redox Reactions Chapter-Wise Test 15

Correct answer Carries: 4.

Wrong Answer Carries: -1.

In \( \ce{HgCl2 + H2S -> Hg + S + 2HCl} \), which species is the reducing agent?

\( \ce{H2S} \) (S: -2 to 0) loses electrons, reducing \( \ce{HgCl2} \) (Hg: +2 to 0).

\( \ce{HgCl2} \)
\( \ce{H2S} \)
\( \ce{Hg} \)
\( \ce{HCl} \)
2

In \( \ce{2NaNO3 -> 2NaNO2 + O2} \), what is the total number of electrons transferred per mole of \( \ce{NaNO3} \)?

N (+5 in \( \ce{NaNO3} \)) to +3 in \( \ce{NaNO2} \): 2 N gain 4 electrons total. Per \( \ce{NaNO3} \) = 4/2 = 2.

1
3
4
2
4

In \( \ce{2HNO3 + 3H2S -> 2NO + 3S + 4H2O} \), what is the total number of electrons transferred per mole of \( \ce{HNO3} \)?

N (+5 in \( \ce{HNO3} \)) to +2 in \( \ce{NO} \): 2 N gain 6 electrons. S (-2 to 0): 3 S lose 6 electrons. Per \( \ce{HNO3} \) = 6/2 = 3.

2
3
4
6
2

Which reaction involves a disproportionation process with a non-metal?

In \( \ce{3S + 6NaOH -> 2Na2S + Na2SO3 + 3H2O} \), S (0) is oxidized to +4 in \( \ce{Na2SO3} \) and reduced to -2 in \( \ce{Na2S} \).

\( \ce{2Na + Cl2 -> 2NaCl} \)
\( \ce{3S + 6NaOH -> 2Na2S + Na2SO3 + 3H2O} \)
\( \ce{Fe + Br2 -> FeBr2} \)
\( \ce{2KI + Cl2 -> 2KCl + I2} \)
2

In the reaction \( \ce{2Cr + 3CuSO4 -> Cr2(SO4)3 + 3Cu} \), what is the oxidizing agent?

The oxidizing agent is reduced. Cu (+2 in \( \ce{CuSO4} \)) becomes 0 in \( \ce{Cu} \), oxidizing Cr (0 to +3).

\( \ce{Cr} \)
\( \ce{CuSO4} \)
\( \ce{Cr2(SO4)3} \)
\( \ce{Cu} \)
2

In the reaction \( \ce{2Na + Br2 -> 2NaBr} \), what is the reducing agent?

The reducing agent is oxidized. Na (0) becomes +1 in \( \ce{NaBr} \), reducing Br (0 to -1).

\( \ce{Br2} \)
\( \ce{Na} \)
\( \ce{NaBr} \)
None of these
2

What is the oxidation number of sulfur in \( \ce{H2SO4} \)?

Let the oxidation number of S be \( x \). H = +1, O = -2. Equation: \( 2(+1) + x + 4(-2) = 0 \). Solving: \( 2 + x - 8 = 0 \), \( x = +6 \).

+6
+4
+2
-2
1

Which reaction is an example of a disproportionation redox process?

In \( \ce{3Br2 + 6NaOH -> 5NaBr + NaBrO3 + 3H2O} \), Br (0) is oxidized to +5 in \( \ce{NaBrO3} \) and reduced to -1 in \( \ce{NaBr} \).

\( \ce{2Na + Cl2 -> 2NaCl} \)
\( \ce{3Br2 + 6NaOH -> 5NaBr + NaBrO3 + 3H2O} \)
\( \ce{Fe + CuSO4 -> FeSO4 + Cu} \)
\( \ce{2KClO3 -> 2KCl + 3O2} \)
2

What is the oxidation number of nitrogen in \( \ce{HNO2} \)?

Let N = \( x \). H = +1, O = -2. Equation: \( +1 + x + 2(-2) = 0 \), \( 1 + x - 4 = 0 \), \( x = +3 \).

+3
+5
-3
+1
1

Which of the following reactions involves both oxidation and reduction?

In \( \ce{2PbO + PbS -> 3Pb + SO2} \), Pb (+2 in \( \ce{PbO} \)) is reduced to 0, and S (-2 in \( \ce{PbS} \)) is oxidized to +4.

\( \ce{HCl + NaOH -> NaCl + H2O} \)
\( \ce{CaCO3 -> CaO + CO2} \)
\( \ce{2PbO + PbS -> 3Pb + SO2} \)
\( \ce{NaCl + KBr -> NaBr + KCl} \)
3

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