Question

Write the balanced equations for the following reactions:

KCN + H₂SO₄ → K₂SO₄ + HCN

Answer 1

Step 1:

Rewrite the given equation as it is

KCN + H₂SO₄ → K₂SO₄ + HCN

Step 2:

Write the number of atoms of each element or group in the unbalanced equation on both sides of the equation.

Element	Number of atoms in reactants	Number of atoms in products
K	1	2
CN (group)	1	1
O	4	4
H	4	4
S	1	1

The number of oxygen atoms involved in different compounds on both sides (reactants and products) are equal. Therefore, balance the number of atoms of the second element, potassium.

Step 3:

To balance K atoms:

Number of atoms of Potassium	In reactants	In products
To begin with	2 (KCN)	2 (in K2SO4)
To balance	1 × 2	2

To equalise the number of potassium atoms, we use 2 as the coefficient of KCN in the reactants. 

Now, the partly balanced equation becomes 

2KCN + H₂SO₄ → K₂SO₄ + 2HCN

Now, count the atoms of each element on both sides of the equation. The number of atoms on both sides are equal. Hence, the balanced equation is

2KCN + H₂SO₄ → KgSO₄ + 2HCN

Now indicate the physical states of the reactants and the products.

2KCN_(aq) + H₂SO_4(aq) → K₂SO_4(aq) + 2HCN_(g)

Answer 2

2KCN + H₂SO₄ → K₂SO4 + 2HCN