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Redox Reactions

Long Answer Type

121.

Write the various steps for balancing a redox equation by oxidation number method.

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Short Answer Type

122. Can you store copper sulphate solutions in a zinc pot?

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123.

Balance the following equation by oxidation number method.

$bold space bold space bold FeCl subscript bold 3 bold space bold plus bold space bold H subscript bold 2 bold S bold space bold space bold rightwards arrow bold space bold space bold space bold FeCl subscript bold 2 bold space bold plus bold space bold HCl bold space bold plus bold space bold S$

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124.

Balance the following equation by oxidation number method:
$straight P space plus space HNO subscript 3 space space rightwards arrow space space space HPO subscript 3 space plus space NO space plus space straight H subscript 2 straight O$

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125.

Balance the following equation by oxidation number method:

$SnO subscript 2 space plus space straight C space rightwards arrow space space space Sn space plus space CO$

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126. Balance the equation by oxidation number method:

bold space bold Fe subscript bold 2 bold O subscript bold 3 bold space bold plus bold space bold C bold space bold space bold rightwards arrow bold space bold space bold space bold space bold Fe bold space bold plus bold space bold CO

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Long Answer Type

127. Balance the euqation by oxidation number method:

straight C subscript 6 straight H subscript 6 space plus space straight O subscript 2 space space space rightwards arrow space space space CO subscript 2 space plus space space straight H subscript 2 straight O

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128. Balance the following,chemical equation by oxidation number method:

$FeS subscript 2 space plus space straight O subscript 2 space space rightwards arrow space space space Fe subscript 2 straight O subscript 3 space plus space SO subscript 2$

(i) The skeleton equation along with oxidation number of each atom is:
+2 -1 0 +3 -2 +4 -2
Fe S₂ + O₂

Fe₂O₃ + SO₂
(O.N. of S in FeS₂ is -1 and not - 2)

(ii) The oxidation number of iron, as well as sulphur, increases from +2 to +3 and -1 to +4 respectively. Since Fe and S must maintain their atomic ratio, the change in oxidation number will be considered together. But, the oxidation number of oxygen decreases from 0 to 2. Thus
O.N: increases 1 per Fe and 5 per S atom

(iii) Equalise the increase/decrease of O:N. multiply FeS₂ by 4 and O₂ by 11.

(iv) On counting and balancing the atoms on both sides, we get the balanced equation as,

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129. Balance the following,chemical equation by oxidation number method:

Mn to the power of 2 plus end exponent space plus space straight S subscript 2 straight O subscript 8 superscript 2 minus end superscript space space space space rightwards arrow space space space space stack MnO subscript 4 superscript minus space plus space HSO subscript 4 superscript minus with left parenthesis acidic space medium right parenthesis below

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130.

Balance the following chemical equation by oxidation number method:
$Zn space plus space NO subscript 3 superscript minus space space rightwards arrow space space space Zn to the power of 2 plus end exponent space plus space left parenthesis NH subscript 4 right parenthesis to the power of plus$ in acidic medium.

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