Redox Reactions Quiz - ICSE Class 11 Chemistry
Free practice quiz: Redox Reactions (ICSE Class 11 Chemistry). 50 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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In the reaction $2KMnO_4 + 10FeSO_4 + 8H_2SO_4 ightarrow K_2SO_4 + 2MnSO_4 + 5Fe_2(SO_4)_3 + 8H_2O$, the equivalent weight of $KMnO_4$ is:
- M/5
- M/3
- M/2
- M/1
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Answer: A. M/5
In this reaction, Mn in $KMnO_4$ changes its oxidation state from +7 to +2 ($MnSO_4$). The change in oxidation state per mole of $KMnO_4$ is 5. Therefore, the number of electrons gained is 5. The equivalent weight of $KMnO_4$ is its molar mass (M) divided by the number of electrons gained, which is M/5.
The oxidation state of bromine in $BrF_3$ is:
- +1
- +2
- +3
- +5
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Answer: C. +3
Fluorine is the most electronegative element and always has an oxidation state of -1 in its compounds, except in $F_2$. Let the oxidation state of bromine be x. In $BrF_3$, we have $x + 3(-1) = 0$. Therefore, $x = +3$.
The oxidation state of chromium in the chromate ion ($CrO_4^{2-}$) is:
- +4
- +5
- +6
- +7
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Answer: C. +6
Let the oxidation state of chromium be x. The oxidation state of oxygen is -2. For the chromate ion ($CrO_4^{2-}$), the sum of oxidation states is equal to the charge of the ion. So, $x + 4(-2) = -2$. $x - 8 = -2$. $x = +6$.
In a redox reaction, the oxidizing agent is:
- Oxidized
- Reduced
- Neither oxidized nor reduced
- Both oxidized and reduced
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Answer: B. Reduced
An oxidizing agent is a substance that accepts electrons from another substance, causing that other substance to be oxidized. In the process, the oxidizing agent itself gains electrons and is therefore reduced.
The equivalent weight of $H_3PO_3$ when it acts as an acid is:
- M/1
- M/2
- M/3
- M/4
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Answer: B. M/2
Phosphorous acid ($H_3PO_3$) is a diprotic acid because one hydrogen atom is directly bonded to phosphorus and is not acidic. The acidic hydrogens are the two bonded to oxygen. The neutralization reaction is $H_3PO_3 + 2NaOH ightarrow Na_2HPO_3 + 2H_2O$. Therefore, its n-factor as an acid is 2. Equivalent weight = Molar mass (M) / n-factor = M/2.