Redox Reactions Chapter-Wise Test 4

Correct answer Carries: 4.

Wrong Answer Carries: -1.

In the reaction \( \ce{2KBr + Cl2 -> 2KCl + Br2} \), what is the oxidizing agent?

\( \ce{Cl2} \) (0) is reduced to -1 in \( \ce{KCl} \), oxidizing Br (-1 to 0).

\( \ce{KBr} \)
\( \ce{Br2} \)
\( \ce{Cl2} \)
\( \ce{KCl} \)
3

In the reaction \( \ce{2KI + Cl2 -> 2KCl + I2} \), what is the oxidizing agent?

\( \ce{Cl2} \) (0) gains electrons to become \( \ce{Cl^-} \) (-1), oxidizing \( \ce{I^-} \) to \( \ce{I2} \).

\( \ce{KI} \)
\( \ce{I2} \)
\( \ce{KCl} \)
\( \ce{Cl2} \)
4

What is the oxidation number of selenium in \( \ce{H2SeO3} \)?

Let Se = \( x \). H = +1, O = -2. Equation: \( 2(+1) + x + 3(-2) = 0 \), \( 2 + x - 6 = 0 \), \( x = +4 \).

+6
+4
+2
-2
2

Which compound contains an element with a fractional oxidation number?

In \( \ce{Fe3O4} \) (FeO·Fe₂O₃), Fe has +2 and +3 states, averaging to +8/3: \( 3x + 4(-2) = 0 \), \( 3x - 8 = 0 \), \( x = +8/3 \).

\( \ce{FeSO4} \)
\( \ce{Fe2O3} \)
\( \ce{Fe3O4} \)
\( \ce{FeCl3} \)
3

What is the oxidation number of nitrogen in \( \ce{NH3} \)?

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

-3
-1
+3
+1
1

In \( \ce{2Na2S2O3 + O2 -> 2Na2SO4} \), what is the total number of electrons transferred per mole of \( \ce{Na2S2O3} \)?

S (+2 avg. in \( \ce{S2O3^2-} \)) to +6 in \( \ce{SO4^2-} \): 4 S lose 4 × (6 - 2) = 16 electrons total. Per \( \ce{Na2S2O3} \) = 16/2 = 8.

4
6
2
8
4

In the reaction \( \ce{2FeCl2 + Cl2 -> 2FeCl3} \), which element is oxidized?

Fe (+2 in \( \ce{FeCl2} \)) becomes +3 in \( \ce{FeCl3} \), losing electrons.

Chlorine
Hydrogen
Iron
None of these
3

What is the oxidation number of sulfur in \( \ce{Na2S2O3} \)?

Let S = \( x \). Na = +1, O = -2. Equation: \( 2(+1) + 2x + 3(-2) = 0 \), \( 2 + 2x - 6 = 0 \), \( 2x = 4 \), \( x = +2 \) (average).

+4
+6
+2
-2
3

Which of the following is a displacement reaction involving redox?

In \( \ce{Fe + 2AgNO3 -> Fe(NO3)2 + 2Ag} \), Fe (0 to +2) is oxidized, and Ag (+1 to 0) is reduced, with Fe displacing Ag.

\( \ce{Fe + 2AgNO3 -> Fe(NO3)2 + 2Ag} \)
\( \ce{2NaCl + F2 -> 2NaF + Cl2} \)
\( \ce{CaO + SiO2 -> CaSiO3} \)
\( \ce{NH3 + H2O -> NH4OH} \)
1

In \( \ce{2Na2S + 3O2 -> 2Na2O + 2SO2} \), what is the total number of electrons transferred per mole of \( \ce{Na2S} \)?

S (-2 in \( \ce{Na2S} \)) to +4 in \( \ce{SO2} \): 2 S lose 2 × (4 - (-2)) = 12 electrons total. Per \( \ce{Na2S} \) = 12/2 = 6.

2
4
8
6
4

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