Chem Help PLEASE?

Question

28.57 liters of perchloric acid solution reacted with an excess amount of magnesium. In the process of this reaction 3270 mL of gas were collected at 25 degrees celcius and 1.5 atm. Calculate:

a. The molar concentration (molarity) of the acid solution;

b. The pH of the acid solution

My main thing is that I don't know how to convert the liters of perchloric acid into moles of perchloric acid to calculate molarity, since it's not at STP and the density isn't given.

Answer 1

STP is for volumes of gases. This problem is about volumes of HClO4 solution. Let the HClO4 solution be called S. 25C = 298K

Mg + 2HClO4 ===> Mg(ClO4)2 + H2(g)

a. 3270mLH2/28.57LS x 273K/298K x 1.5atm/1atm x 1molH2/22,400mLH2 x 2molHClO4/1molH2 = 0.01404 mole HClO4 per L solution (molarity)

b. pH = -Log[H+]

Log(0.01404) = -1.852

pH = +1.852