The major species in solution when solid ammonium bromate is dissolved in water is shown below
It actually depends on the percentage of the concentration give. Percentages can be expressed as %mass/mass, %volume/volume or %mass/volume. To keep things simple, let's just assume that it is in %volume/volume. Thus, 13% of 520 mL is pure acid.
Volume of pure acid = 520*0.13 = 67.6 mL
They will melt at the same rate because they contain the same matter
hope this helps and good luck on your project!!!!