Question

Mg + HNO3 -----> Mg(NO3)2 + N2O + H2O

Balance this equation by ion-electron method only

Answer 1

mg + 4HNO3-------- MG (NO3)2 +2N2O+2H2O

Answer 2

Explanation:

Dear Student,

Please find below the solution to the asked query:

Mg +HNO3 → Mg(NO3)2 +N2O + H2O

To balance this equation by electron ion method

Step1: We write the redox equation in ionic form

Mg + H+ + NO3- → Mg 2+ + N2O + H2O

Step 2 : The reaction is splitted into oxidation half and reduction half reaction

Mg → Mg 2+

NO3- → N2O

Step 3: We balance the atoms of each half reaction except H and O using simple multiples

Mg → Mg 2+

2NO3- → N2O

Step 4:Balancing of H and O

1) For acidic and neutral solutions : H2O is added on the side deficient in O and H+ is added on the side deficient in H+

2) For basic: For each excess O , one H2O is added on the same side and OH- ion to the other side to balance H

Here

H+ is added on the side deficient in H+ and H2O is added on the side deficient in O

Mg → Mg 2+

10 H+ + 2NO3- → N2O + 5H2O

Step 5: Electrons are added to the sides where electrons are deficient

Mg → Mg 2+ +2e [Change in oxidation state Mg → Mg 2 +is 2]

8e + 10 H+ + 2NO3- → N2O + 5H2O [ Change in oxidation state 2HNO3 → N2O is 10-2 =8]

Step 6: The no.of electrons in both equations are equalised

[ Mg → Mg 2+ +2e ] x 4

[ 8e + 10 H+ + 2NO3- → N2O + 5H2O] x1

Step 7: The two balanced half reactions are added and the common terms are cancelled

4 Mg → 4 Mg 2+ + 8e

8e + 10 H+ + 2NO3- → N2O + 5H2O

Adding we get

4 Mg + 10 H+ + 2NO3- → 4 Mg 2+ + N2O + 5H2O

Step 8: Converting the ionic equation into molecular equation and adding the spectator ions we get

4 Mg + 10 H+ + 2NO3- + 8 NO3- → 4 Mg 2+ + N2O + 5H2O + 8NO3-[NO3- is the spectator ion here which is added on both sides of the equation]

Therefore we get: 4 Mg + 10HNO3 → 4 Mg(NO3)2 +N2O + 5H2O

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