Redox Reactions Chapter-Wise Test 17

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What is the oxidation number of sulfur in \( \ce{H2S} \)?

Let S = \( x \). H = +1. Equation: \( 2(+1) + x = 0 \), \( 2 + x = 0 \), \( x = -2 \).

-2
+2
+4
0
1

Which reaction does not involve a redox process?

In \( \ce{MgSO4 + 2NaOH -> Mg(OH)2 + Na2SO4} \), no element changes oxidation state; it’s a double displacement reaction.

\( \ce{2Na + 2H2O -> 2NaOH + H2} \)
\( \ce{Fe + 2HCl -> FeCl2 + H2} \)
\( \ce{MgSO4 + 2NaOH -> Mg(OH)2 + Na2SO4} \)
\( \ce{2H2O2 -> 2H2O + O2} \)
3

Which of the following reactions demonstrates the removal of hydrogen, indicating an oxidation process?

Oxidation can involve hydrogen loss. In \( \ce{2H2S + O2 -> 2S + 2H2O} \), H₂S loses hydrogen to form S, indicating oxidation.

\( \ce{2H2S + O2 -> 2S + 2H2O} \)
\( \ce{H2 + Cl2 -> 2HCl} \)
\( \ce{2Na + 2H2O -> 2NaOH + H2} \)
\( \ce{Fe + H2SO4 -> FeSO4 + H2} \)
1

In the reaction \( \ce{H2S + Cl2 -> 2HCl + S} \), which element is oxidized?

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

Sulfur
Chlorine
Hydrogen
None of these
1

Which of the following reactions shows the gain of electrons by a species, indicating reduction?

Reduction involves electron gain. In \( \ce{2FeCl3 + SnCl2 -> 2FeCl2 + SnCl4} \), Fe (+3) gains an electron to become Fe (+2).

\( \ce{2FeCl3 + SnCl2 -> 2FeCl2 + SnCl4} \)
\( \ce{2Na + O2 -> Na2O2} \)
\( \ce{H2S + I2 -> 2HI + S} \)
\( \ce{2NH3 -> N2 + 3H2} \)
1

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

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

Manganese
Oxygen
Sulfur
Hydrogen
3

In the reaction \( \ce{PbS + 4H2O2 -> PbSO4 + 4H2O} \), which element is reduced?

O (-1 in \( \ce{H2O2} \)) becomes -2 in \( \ce{H2O} \), gaining electrons.

Lead
Oxygen
Sulfur
Hydrogen
2

In the reaction \( \ce{Cl2 + 2KBr -> 2KCl + Br2} \), which element is oxidized?

Oxidation involves electron loss. Br (-1 in \( \ce{KBr} \)) becomes 0 in \( \ce{Br2} \), losing electrons.

Bromine
Chlorine
Potassium
None of these
1

What is the oxidation number of nitrogen in \( \ce{N2H4} \)?

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

+2
-2
-1
+4
2

In which compound does oxygen have an oxidation number of +2?

In \( \ce{OF2} \), O is less electronegative than F (-1). Equation: \( x + 2(-1) = 0 \), \( x = +2 \).

\( \ce{H2O} \)
\( \ce{H2O2} \)
\( \ce{OF2} \)
\( \ce{KO2} \)
3

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