Answer: 1. A2 + B2 => 2 AB
2. 2 A + 3 B => A2B3
3. 2 A + 3 B2 => 2 AB3
4. A2 + 2 B2 => 2 AB2
5. 2 A2 + 3 B2 => 2 A2B3
Explanation: So to make the equations balance we will put numerical coefficients on each variable so that the total number of atoms will be equal on each side.
For number 1 we will put 2 on AB to balance the reactant. For number 2, we will write 2 on A and 3 in B in the reactant side. For number 3, write 2 on A and 3 on B2 in the reactant and 2 on AB3 in the product side. For number 4, the coeffecients are 1:2:2 and lastly on number 5 the coeffencients are 2:3:2.