Answer:
9
Explanation:
To balance the equation, we need to supply the number of missing coefficients.
There are 2 moles of aluminium on the right hand side, so automatically we need to multiply the number of moles of aluminium by 2 on the left hand side.
There are 3 sulphate ions on the right hand side so we need to multiply the number on the left by 3.
And lastly since we have 6 hydrogen molecules on the left hand side now, we need to multiply the hydrogen on the right hand side by 3 to give 6
The set of coefficients = 2 3 1 3
Adding all thus yields 9