Redox Reactions Chapter-Wise Test 18

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which reaction represents a decomposition redox process?

In \( \ce{2Ag2O -> 4Ag + O2} \), Ag (+1) is reduced to 0, and O (-2) is oxidized to 0.

\( \ce{CaCO3 -> CaO + CO2} \)
\( \ce{2Ag2O -> 4Ag + O2} \)
\( \ce{NH4Cl -> NH3 + HCl} \)
\( \ce{Na2CO3 -> Na2O + CO2} \)
2

In \( \ce{TeO2 + 2H2 -> Te + 2H2O} \), which species is reduced?

\( \ce{TeO2} \) (Te: +4 to 0) gains electrons, reduced by \( \ce{H2} \) (0 to +1).

\( \ce{H2} \)
\( \ce{TeO2} \)
\( \ce{Te} \)
\( \ce{H2O} \)
2

In \( \ce{2FeSO4 + H2O2 + H2SO4 -> Fe2(SO4)3 + 2H2O} \), which species is reduced?

\( \ce{H2O2} \) (O: -1 to -2 in \( \ce{H2O} \)) gains electrons, oxidizing Fe (+2 to +3).

\( \ce{FeSO4} \)
\( \ce{Fe2(SO4)3} \)
\( \ce{H2SO4} \)
\( \ce{H2O2} \)
4

In the reaction \( \ce{5H2S + 2KMnO4 + 3H2SO4 -> 5S + 2MnSO4 + K2SO4 + 8H2O} \), which element is oxidized?

S (-2 in \( \ce{H2S} \)) becomes 0 in \( \ce{S} \), losing electrons.

Manganese
Hydrogen
Sulfur
Oxygen
3

What is the oxidation number of rhenium in \( \ce{ReO3} \)?

Let Re = \( x \). O = -2. Equation: \( x + 3(-2) = 0 \), \( x - 6 = 0 \), \( x = +6 \).

+6
+4
+2
+3
1

In \( \ce{2As + 3H2S -> As2S3 + 3H2} \), what is the total number of electrons transferred per mole of \( \ce{As} \)?

As (0 to +3 in \( \ce{As2S3} \)): 2 As lose 6 electrons total. Per \( \ce{As} \) = 6/2 = 3 electrons.

2
3
4
6
2

In the reaction \( \ce{Pb + PbO2 + 2H2SO4 -> 2PbSO4 + 2H2O} \), what is the oxidizing agent?

\( \ce{PbO2} \) (Pb: +4 to +2) accepts electrons from Pb (0 to +2), acting as the oxidizing agent.

\( \ce{Pb} \)
\( \ce{H2SO4} \)
\( \ce{PbSO4} \)
\( \ce{PbO2} \)
4

Which compound contains sulfur with an oxidation number higher than in \( \ce{SO2} \)?

S in \( \ce{SO2} \): +4. In \( \ce{SO3} \): \( x + 3(-2) = 0 \), \( x = +6 \), which is higher.

\( \ce{H2S} \)
\( \ce{SCl2} \)
\( \ce{SO3} \)
\( \ce{S2O3^2-} \)
3

In \( \ce{2CuCl2 + 4KI -> 2CuI + 4KCl + I2} \), which species is oxidized?

I (-1 in \( \ce{KI} \)) becomes 0 in \( \ce{I2} \), losing electrons; Cu (+2 to +1) is reduced.

\( \ce{CuCl2} \)
\( \ce{CuI} \)
\( \ce{KCl} \)
\( \ce{KI} \)
4

Which of the following reactions involves a redox process with a non-metal?

In \( \ce{S8 + 8O2 -> 8SO2} \), S (0) is oxidized to +4, and O (0) is reduced to -2.

\( \ce{CaO + H2O -> Ca(OH)2} \)
\( \ce{NaCl + KNO3 -> NaNO3 + KCl} \)
\( \ce{HCl + NH3 -> NH4Cl} \)
\( \ce{S8 + 8O2 -> 8SO2} \)
4

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