The following reactions take place when nitric acid is added to zinc - Scottish Highers Chemistry - Question 4 - 2019
Question 4
The following reactions take place when nitric acid is added to zinc.
$$NO_3^{-} (aq) + 4H^{+}(aq) + 3e^{-} \rightarrow NO(g) + 2H_2O(l)$$
$$Zn(s) \rightarrow Zn^{... show full transcript
Worked Solution & Example Answer:The following reactions take place when nitric acid is added to zinc - Scottish Highers Chemistry - Question 4 - 2019
Step 1
Identify the half-reactions
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Answer
The relevant half-reactions from the provided information are:
Reduction of nitrate ion:
NO3−+4H++3e−→NO+2H2O
Oxidation of zinc:
Zn→Zn2++2e−
Step 2
Balance the electrons
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Answer
To find the relationship between the reactants, we need to balance the electrons. The reduction reaction consumes 3 electrons while the oxidation reaction produces 2 electrons.
To balance these, we can find the least common multiple (LCM) of 2 and 3, which is 6.
Thus, we multiply the half-reactions as follows:
The reduction reaction is multiplied by 2, giving 6 electrons:
2NO3−+8H++6e−→2NO+4H2O
The oxidation reaction is multiplied by 3, also giving 6 electrons:
3Zn→3Zn2++6e−
Step 3
Determine moles of Zn oxidized per mole of NO3-
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Answer
From the balanced half-reactions, 2 moles of nitrate ions oxidize 3 moles of zinc. Therefore, 1 mole of nitrate ion would oxidize:
23=1.5molesofZn
Hence, the answer is 1.5.
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