If you want to express the concentration in terms of percent mass, then you would have to divide the mass of solute to the mass of solution, then multiply it by 100.
Mass of solute = 8.40 g Mass of solution = 8.40+94.60 = 103 g
In balanced equation there are same number of atoms in each element on both sides of the equation. unbalanced equation is when there are different number of atoms in each element on the both sides
