Balance the following equations stepwise:
a. H2S2O7 (l) + H2O (l) → H2SO4 (l)
  1. First, let’s write the equation as shown below:
    H2S2O7 + H2O → H2SO4
  2. Write the number of atoms in the unbalanced equation:
    Element No. of atoms in reactants No. of atoms in products
    H 4 2
    S 2 1
    O 8 4
    Total 14 7
  3. Now, equalise the number of hydrogen atoms of products by using a factor of 2:
    Element No. of atoms in reactants No. of atoms in products
    H 4 2 × 2 = 4
    S 2 1 × 2 = 2
    O 8 4 × 2 = 8
    Total 14 14
  4. Now, the equation becomes:
    H2S2O7 + H2O → 2H2SO4
  5. Count the number of atoms of each element on each side. We find that the number of atoms is same on each side. Hence, this is a balanced equation.
  6. Indicate the physical states of reactants and products and write the final balanced equation as:
    H2S2O7 (l) + H2O (l) → 2H2SO4 (l)
b. SO2 (g) + H2S (aq) → S (s) + H2O (l)
  1. First, let’s write the equation as shown below:
    SO2 + H2S → S + H2O
  2. Write the number of atoms in the unbalanced equation:
    Element No. of atoms in reactants No. of atoms in products
    S 2 1
    O 2 1
    H 2 2
    Total 6 4
  3. Now, equalise the number of sulphur atoms of products by using a factor of 2 for sulphur:
    Element No. of atoms in reactants No. of atoms in products
    S 2 1 × 2 = 2
    O 2 1
    H 2 2
    Total 6 5
  4. Now, the equation becomes:
    SO2 + H2S → 2S + H2O
  5. Now, equalise the number of oxygen atoms of products by using a factor of 2 for H2O:
    Element No. of atoms in reactants No. of atoms in products
    S 2 2
    O 2 1 × 2 = 2
    H 2 2 × 2 = 4
    Total 6 8
  6. Now, the equation becomes:
    SO2 + H2S → 2S + 2H2O
  7. Now, equalise the number of hydrogen atoms of reactants by using a factor of 2 for H2S:
    Element No. of atoms in reactants No. of atoms in products
    S 3 2
    O 2 2
    H 2 × 2 = 4 4
    Total 9 8
  8. Now, the equation becomes:
    SO2 + 2H2S → 2S + 2H2O
  9. Now, equalise the number of sulphur atoms of products by using a factor of 3 for S:
    Element No. of atoms in reactants No. of atoms in products
    S 3 3
    O 2 2
    H 2 × 2 = 4 4
    Total 9 9
  10. Now, the equation becomes:
    SO2 + 2H2S → 3S + 2H2O
  11. Count the number of atoms of each element on each side. We find that the number of atoms is same on each side. Hence, this is a balanced equation.
  12. Indicate the physical states of reactants and products and write the final balanced equation as:
    SO2 (g) + 2H2S (aq) → 3S (s) + 2H2O (s)
c. Ag (s) + HCl (aq) → AgCl ↓ + H2 ↑
  1. First, let’s write the equation as shown below:
    Ag + HCl → AgCl + H2
  2. Write the number of atoms in the unbalanced equation:
    Element No. of atoms in reactants No. of atoms in products
    Ag 1 1
    H 1 2
    Cl 1 1
    Total 3 4
  3. Now, equalise the number of hydrogen atoms of reactants by using a factor of 2 for HCl:
    Element No. of atoms in reactants No. of atoms in products
    Ag 1 1
    H 1 × 2 = 2 2
    Cl 1 × 2 = 2 1
    Total 5 4
  4. Now, the equation becomes:
    Ag + 2HCl → AgCl + H2
  5. Now, equalise the number of chlorine atoms of products by using a factor of 2 for AgCl:
    Element No. of atoms in reactants No. of atoms in products
    Ag 1 1 × 2 = 2
    H 2 2
    Cl 2 1 × 2 = 2
    Total 5 6
  6. Now, the equation becomes:
    Ag + 2HCl → 2AgCl + H2
  7. Now, equalise the number of silver atoms of reactants by using a factor of 2 for Ag:
    Element No. of atoms in reactants No. of atoms in products
    Ag 1 × 2 = 2 2
    H 2 2
    Cl 2 2
    Total 6 6
  8. Now, the equation becomes:
    2Ag + 2HCl → 2AgCl + H2
  9. Count the number of atoms of each element on each side. We find that the number of atoms is same on each side. Hence, this is a balanced equation.
  10. Indicate the physical states of reactants and products and write the final balanced equation as:
    2Ag (s) + 2HCl (aq) → 2AgCl ↓ + H2 ↑
d. NaOH (aq) + H2SO4 (aq) → Na2SO4 (aq) + H2O (l)
  1. First, let’s write the equation as shown below:
    NaOH + H2SO4 → Na2SO4 + H2O
  2. Write the number of atoms in the unbalanced equation:
    Element No. of atoms in reactants No. of atoms in products
    Na 1 2
    S 1 1
    O 5 5
    H 3 2
    Total 10 10
  3. Now, equalise the number of sodium atoms of reactants by using a factor of 2 for NaOH:
    Element No. of atoms in reactants No. of atoms in products
    Na 2 2
    S 1 1
    O 6 5
    H 4 2
    Total 13 10
  4. Now, the equation becomes:
    2NaOH + H2SO4 → Na2SO4 + H2O
  5. Now, equalise the number of oxygen atoms of products by using a factor of 2 for H2O:
    Element No. of atoms in reactants No. of atoms in products
    Na 2 2
    S 1 1
    O 6 6
    H 4 4
    Total 13 13
  6. Now, the equation becomes:
    2NaOH + H2SO4 → Na2SO4 + 2H2O
  7. Count the number of atoms of each element on each side. We find that the number of atoms is same on each side. Hence, this is a balanced equation.
  8. Indicate the physical states of reactants and products and write the final balanced equation as:
    2NaOH (aq) + H2SO4 (aq) → Na2SO4 (aq) + 2H2O (l)
  Home

This page was last modified on
12 August 2019 at 20:31

⇈