What is the mass of the reaction mixture. Assume the density of the mixture is 1.03g/mL?

Question

A student determined the heat of neutralization of perchloric acid mixed with sodium hydroxide solution. 40 milliliters of 1.00 M HClO_4 were added to 40.5 mL of 1.00 M NaOH solution

Answer 1

40+40.5 = 80.5 (ml)
80.5*1.03 = 82.9 (g)
That is the mass of the reaction mixture.