Redox Reactions Chapter-Wise Test 16

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What is the oxidation number of antimony in \( \ce{SbF5} \)?

Let Sb = \( x \). F = -1. Equation: \( x + 5(-1) = 0 \), \( x - 5 = 0 \), \( x = +5 \).

+5
+3
+2
-5
1

What is the oxidation number of tungsten in \( \ce{WO3} \)?

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

+4
+6
+2
+3
2

In the reaction \( \ce{2KI + Br2 -> 2KBr + I2} \), which species is the reducing agent?

\( \ce{KI} \) (I: -1 to 0 in \( \ce{I2} \)) loses electrons, reducing \( \ce{Br2} \) (0 to -1).

\( \ce{Br2} \)
\( \ce{KBr} \)
\( \ce{I2} \)
\( \ce{KI} \)
4

In \( \ce{2NiS + 3O2 -> 2NiO + 2SO2} \), which species is oxidized?

\( \ce{NiS} \) contains S (-2 to +4 in \( \ce{SO2} \)) losing electrons; Ni (+2 to +2) unchanged, S is oxidized.

\( \ce{NiO} \)
\( \ce{O2} \)
\( \ce{SO2} \)
\( \ce{NiS} \)
4

In the reaction \( \ce{2MnO2 + 2KOH + O2 -> 2K2MnO4 + H2} \), which species is reduced?

Reduction involves electron gain. O (0 in \( \ce{O2} \)) becomes -1 in \( \ce{H2} \) (via intermediate steps), gaining electrons.

\( \ce{MnO2} \)
\( \ce{O2} \)
\( \ce{KOH} \)
\( \ce{K2MnO4} \)
2

What is the oxidation number of chlorine in \( \ce{Cl2O7} \)?

Let Cl = \( x \). O = -2. Equation: \( 2x + 7(-2) = 0 \), \( 2x - 14 = 0 \), \( x = +7 \).

+5
+3
+1
+7
4

In \( \ce{2MnO4^- + 5C2O4^2- + 16H^+ -> 2Mn^2+ + 10CO2 + 8H2O} \), which species contains the element oxidized?

C (+3 in \( \ce{C2O4^2-} \)) to +4 in \( \ce{CO2} \) is oxidized; Mn (+7 to +2) is reduced.

\( \ce{MnO4^-} \)
\( \ce{Mn^2+} \)
\( \ce{C2O4^2-} \)
\( \ce{CO2} \)
3

In the reaction \( \ce{2Na + Cl2 -> 2NaCl} \), what is the oxidizing agent?

The oxidizing agent accepts electrons. \( \ce{Cl2} \) (0) gains electrons to become \( \ce{Cl^-} \) (-1), oxidizing Na.

\( \ce{Cl2} \)
\( \ce{Na} \)
\( \ce{NaCl} \)
None of these
1

In \( \ce{2K2Cr2O7 + 14HCl -> 2CrCl3 + 2KCl + 3Cl2 + 7H2O} \), how many electrons are transferred?

Cr (+6 in \( \ce{Cr2O7^2-} \)) to +3 in \( \ce{CrCl3} \): 4 Cr gain 12 electrons. Cl (-1 to 0): 6 Cl lose 12 electrons. Total = 12.

8
10
6
12
4

Which of the following is a redox reaction?

In \( \ce{CuO + H2 -> Cu + H2O} \), Cu (+2 to 0) is reduced, and H (0 to +1) is oxidized.

\( \ce{HCl + NaOH -> NaCl + H2O} \)
\( \ce{NaCl + AgNO3 -> AgCl + NaNO3} \)
\( \ce{CuO + H2 -> Cu + H2O} \)
\( \ce{CaCO3 -> CaO + CO2} \)
3

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