The reaction between arsenic pentasulfide (As₂S₅) and nitric acid (HNO₃) is a complex redox reaction that produces arsenic acid (H₃AsO₄), sulfur (S), and nitrogen dioxide (NO₂). Here's how to balance the reaction:

Unbalanced Equation:

As₂S₅ + HNO₃ → H₃AsO₄ + S + NO₂ + H₂O

Balancing Steps:

1. Balance As: There are 2 As atoms on the left and 1 on the right. Multiply H₃AsO₄ by 2:

As₂S₅ + HNO₃ → 2H₃AsO₄ + S + NO₂ + H₂O

2. Balance S: There are 5 S atoms on the left and 1 on the right. Multiply S by 5:

As₂S₅ + HNO₃ → 2H₃AsO₄ + 5S + NO₂ + H₂O

3. Balance N: There is 1 N atom on the left and 1 on the right.

4. Balance O: There are 3 O atoms on the left and 13 on the right. Adjust the HNO₃ coefficient to balance the O atoms:

As₂S₅ + 10HNO₃ → 2H₃AsO₄ + 5S + 10NO₂ + H₂O

5. Balance H: There are 10 H atoms on the left and 8 on the right. Add 2 H₂O molecules to the right side:

As₂S₅ + 10HNO₃ → 2H₃AsO₄ + 5S + 10NO₂ + 2H₂O

Balanced Equation:

As₂S₅ + 10HNO₃ → 2H₃AsO₄ + 5S + 10NO₂ + 2H₂O

Important Note: This reaction is quite complex and may proceed through several steps. The balanced equation represents the overall stoichiometry of the reaction.