
: In which of the following reactions does conc. ${{\text{H}}_2}{\text{S}}{{\text{O}}_4}$ act as an oxidizing agent?
A)${\text{ZnO + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4}$
B)${\text{KBr + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4}$
C)${\text{NaCl + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4}$
D) None of these
Answer
487.2k+ views
Hint:
The reaction between salts and sulphuric acid results in a displacement reaction. In such reactions the oxidation number of the elements does not change.
Complete step by step answer:
The oxidizing agent increases the oxidation state of the other substance in the chemical reaction. Conc. Sulphuric acid is a strong oxidizing reagent. But when it reacts with salts it either does not give reaction or shows displacement reaction. The reactions are as follows-
1. When zinc oxide reacts with conc. Sulphuric acid, zinc sulphate (salt) and water is formed as zinc displaces hydrogen due to high reactivity.
$ \Rightarrow $ ${\text{ZnO + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{ZnS}}{{\text{O}}_4} + {{\text{H}}_2}{\text{O}}$
The oxidation number of zinc does not change in the above reaction. The oxidation number of zinc in zinc oxide is $ + 2$ as the oxygen atom has $ - 2$ state in oxides so the molecule is neutral. In zinc sulphate the oxidation number of zinc is-
$ \Rightarrow x + \left( { - 2} \right) = 0 \Rightarrow x = + 2$ $ \Rightarrow x + \left( { - 2} \right) = + 2$
2. When potassium bromide reacts with conc. Sulphuric acid, potassium displaces hydrogen to form potassium sulphate as it is more reactive than hydrogen.
$ \Rightarrow 2{\text{KBr + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {{\text{K}}_2}{\text{S}}{{\text{O}}_4} + 2{\text{HBr}}$
Here also the oxidation number of potassium does not change and remains $ + 1$ after the reaction.
The oxidation state of potassium in potassium bromide is-$ \Rightarrow 2x + 2\left( { - 1} \right) = 0 \Rightarrow x = + 1$
The oxidation state of potassium in potassium sulphate is-$ \Rightarrow 2x + \left( { - 2} \right) = 0 \Rightarrow x = + 1$
3. When sodium chloride is reacted with conc. Sulphuric acid, it gives no reaction as sodium chloride is neutral salt.
$ \Rightarrow {\text{NaCl + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{no reaction}}$
Since no reaction happens so the oxidation state of sodium does not change.
Hence , in the above reactions the sulphuric acid does not act as an oxidizing agent.
So the correct option is ‘D’.
Note:
Sulphuric acid has many uses besides acting as an oxidizing agent which are-
1. As a dehydrating agent it absorbs water from sugar, starch, paper and wood.
2. In manufacturing of paint.
3. In manufacturing of explosives such as nitroglycerine.
5. In petroleum refining.
The reaction between salts and sulphuric acid results in a displacement reaction. In such reactions the oxidation number of the elements does not change.
Complete step by step answer:
The oxidizing agent increases the oxidation state of the other substance in the chemical reaction. Conc. Sulphuric acid is a strong oxidizing reagent. But when it reacts with salts it either does not give reaction or shows displacement reaction. The reactions are as follows-
1. When zinc oxide reacts with conc. Sulphuric acid, zinc sulphate (salt) and water is formed as zinc displaces hydrogen due to high reactivity.
$ \Rightarrow $ ${\text{ZnO + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{ZnS}}{{\text{O}}_4} + {{\text{H}}_2}{\text{O}}$
The oxidation number of zinc does not change in the above reaction. The oxidation number of zinc in zinc oxide is $ + 2$ as the oxygen atom has $ - 2$ state in oxides so the molecule is neutral. In zinc sulphate the oxidation number of zinc is-
$ \Rightarrow x + \left( { - 2} \right) = 0 \Rightarrow x = + 2$ $ \Rightarrow x + \left( { - 2} \right) = + 2$
2. When potassium bromide reacts with conc. Sulphuric acid, potassium displaces hydrogen to form potassium sulphate as it is more reactive than hydrogen.
$ \Rightarrow 2{\text{KBr + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {{\text{K}}_2}{\text{S}}{{\text{O}}_4} + 2{\text{HBr}}$
Here also the oxidation number of potassium does not change and remains $ + 1$ after the reaction.
The oxidation state of potassium in potassium bromide is-$ \Rightarrow 2x + 2\left( { - 1} \right) = 0 \Rightarrow x = + 1$
The oxidation state of potassium in potassium sulphate is-$ \Rightarrow 2x + \left( { - 2} \right) = 0 \Rightarrow x = + 1$
3. When sodium chloride is reacted with conc. Sulphuric acid, it gives no reaction as sodium chloride is neutral salt.
$ \Rightarrow {\text{NaCl + }}{{\text{H}}_2}{\text{S}}{{\text{O}}_4} \to {\text{no reaction}}$
Since no reaction happens so the oxidation state of sodium does not change.
Hence , in the above reactions the sulphuric acid does not act as an oxidizing agent.
So the correct option is ‘D’.
Note:
Sulphuric acid has many uses besides acting as an oxidizing agent which are-
1. As a dehydrating agent it absorbs water from sugar, starch, paper and wood.
2. In manufacturing of paint.
3. In manufacturing of explosives such as nitroglycerine.
5. In petroleum refining.
Recently Updated Pages
The correct geometry and hybridization for XeF4 are class 11 chemistry CBSE

Water softening by Clarks process uses ACalcium bicarbonate class 11 chemistry CBSE

With reference to graphite and diamond which of the class 11 chemistry CBSE

A certain household has consumed 250 units of energy class 11 physics CBSE

The lightest metal known is A beryllium B lithium C class 11 chemistry CBSE

What is the formula mass of the iodine molecule class 11 chemistry CBSE

Trending doubts
10 examples of friction in our daily life

One Metric ton is equal to kg A 10000 B 1000 C 100 class 11 physics CBSE

Difference Between Prokaryotic Cells and Eukaryotic Cells

State and prove Bernoullis theorem class 11 physics CBSE

What organs are located on the left side of your body class 11 biology CBSE

How many valence electrons does nitrogen have class 11 chemistry CBSE
