7.Answer the following with justification/showingcalculations: a) What is the pH

Question

7.Answer the following with justification/showingcalculations:

a) What is the pH of 1x10-9 M HCl?

b) If the concentration of H+ in a solution is 10-3 M, whatwill the concentration of OH- be in the same

solution at 25°C?

c) How many ml of a 0.2 M NaOH solution are required to bringthe pH of 20 ml of a 0.4 M HCl solution

to 7.0?

d) Physiological pH is 7.4. What is the hydrogen ionconcentration of a solution at physiological pH?

e) Express the concentration of a 2.0 M NaOH solution as a %(w/v) solution.

Explanation / Answer

a) HCl is a strong acid. [H+] = 1.0e-9 pH = -log H = -log (1.0e-9) = 9 b) [H+][O-] = 1.0e-14 [1E-3)(x) = 1.0e-14 x = [oh-]= 1E-11 M c) Noticed that the acid concentration is twice that of the base(.4 vs .2 M). A neutral solution (ph 7) can be achieved if you justadd twice the base solution to the acid solution. answer: 2 x 20 mL = 40 mL d) [H+] = 10^-pH = 10^-7.4 = 3.98e-8 M e) MOlarity = moles / L 2 M = 2 moles / 1 L 2 moles NaOH (40 g/1 mol) = 80 grams NaOH 1 L = 1000 mL (80/1000 ) x 100 = 8%

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