Question

Balance the following chemical reaction: \( Pb(NO_3)_2 + KI \longrightarrow PbI_2 + KNO_3 \)

Hint:

In double displacement reactions, try balancing the polyatomic ions (like \( NO_3 \)) as single units first to simplify the process.

Answer 1

Given Unbalanced Reaction:
\[ Pb(NO_3)_2 + KI \longrightarrow PbI_2 + KNO_3 \]

Step 1: Count the number of atoms on both sides
Left side:
Pb = 1
(NO₃) = 2 groups
K = 1
I = 1 Right side:
Pb = 1
I = 2
K = 1
(NO₃) = 1 group
Iodine and nitrate groups are not balanced.

Step 2: Balance Iodine (I)
Since PbI₂ contains 2 iodine atoms, we need 2 KI on the left side. \[ Pb(NO_3)_2 + 2KI \longrightarrow PbI_2 + KNO_3 \] Now I atoms are balanced (2 on both sides).

Step 3: Balance Potassium (K)
There are 2 potassium atoms on the left (from 2KI), so place coefficient 2 before KNO₃. \[ Pb(NO_3)_2 + 2KI \longrightarrow PbI_2 + 2KNO_3 \]

Step 4: Check Nitrate Groups (NO₃)
Left side: 2 nitrate groups
Right side: 2 nitrate groups (from 2KNO₃) Balanced.

Step 5: Final Check
Pb = 1 on both sides ✔
K = 2 on both sides ✔
I = 2 on both sides ✔
(NO₃) = 2 on both sides ✔

Balanced Chemical Equation: \[ \boxed{Pb(NO_3)_2 + 2KI \longrightarrow PbI_2 + 2KNO_3} \]