Answer:
2 AsCl₃ + 3 H₂S → As₂S₃ + 6 HCl
Step-by-step explanation:
When we balance a chemical equation, what we are trying to do is to achieve the same number of atoms for each element on both sides of the arrow. On the right of the arrow is where we can find the products, while the reactants are found on the left of the arrow.
We usually balance O and H atoms last.
AsCl₃ + H₂S → As₂S₃ +HCl
reactants
As --- 1
Cl --- 3
H --- 2
S --- 1
products
As --- 2
Cl --- 1
H --- 1
S --- 3
2 AsCl₃ + H₂S → As₂S₃ +HCl
reactants
As --- 2
Cl --- 6
H --- 2
S --- 1
products
As --- 2
Cl --- 1
H --- 1
S --- 3
The number of As atoms is now balanced.
2 AsCl₃ + 3 H₂S → As₂S₃ +HCl
reactants
As --- 2
Cl --- 6
H --- 6
S --- 3
products
As --- 2
Cl --- 1
H --- 1
S --- 3
The number of S atoms is now equal on both sides.
2 AsCl₃ + 3 H₂S → As₂S₃ + 6 HCl
reactants
As --- 2
Cl --- 6
H --- 6
S --- 3
products
As --- 2
Cl --- 6
H --- 6
S --- 3
The equation is now balanced.