I just really don\'t understand these. I tried looking through the textbook, but

Question

I just really don't understand these. I tried looking through the textbook, but I'm still stuck. If someone could provide me with a step by step explanation, I will be really grateful. thanks in advance.

1) The pH range given in textbooks is typically 0 - 14. Concentrated acids and bases may fall outside this range. Calculate the pH of hydrochloric acid, if the solution is sold as 33 % by weight (33 g HCl / 100 g solution) with a density of 1.16 g/mL.

2) Calculate the pH of an 0.015 M solution of HCl (hydrochloric acid).

Explanation / Answer

(1) Consider 1 L = 1000 mL of solution

Mass of solution = volume x density

= 1000 x 1.16 = 1160 g


Mass of HCl = 33% of mass of solution

= 33/100 x mass of solution

= 33/100 x 1160 = 382.8 g


Moles of HCl = mass/molar mass of HCl

= 382.8/36.46 = 10.499 mol


[H+] = [HCl] = moles/volume = 10.499/1 = 10.499 M

pH = -log[H+] = -log(10.499) = -1.02


(2) [H+] = [HCl] = 0.015 M

pH = -log[H+] = -log(0.015) = 1.82

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