Calculate the pH of a solution that has a hydrochloric acid (HC1) concentration

Question

Calculate the pH of a solution that has a hydrochloric acid (HC1) concentration of 0.02 moled/L. pKa of hypochlorous acid 7.60. What is Ka (express answer in decimal form). Calcium fluoride (CaF2) dissociates in water per the equation shown below. In a pure solution of CaF2: what would the fluoride concentration be (in moles/L) when the Calcium concentration is 0.25 moles/L? CaF2 rightarrow Ca2+ + 2F- What is the partial pressure of atmospheric nitrogen (in atm) at an elevation of 2000 m? Assume air is 79% nitrogen and 21% oxygen/

Explanation / Answer

Ans:                             pH = -log10[H+]

Hydrogen ion concentration = [H+] = 0.02 mol L-1

pH = -log10[0.02]

pH = 1.698

Ans: pka = -log10[Ka]

7.60 = -log10[Ka]

Ka = 10-7.60 = 2.511 * 10-8

CaF2        Ca2+ + 2F-

Ans: fluoride concentration will be = 2 * 0.25 = 0.50 moles/L

Ans: Air pressure above sea level can be calculated as

p = 101325 (1 - 2.25577 10-5 h)5.25588    

at 2000 m

p = 101325 (1 - 2.25577 10-5 * 2000)5.25588    

p = 101325 (1 – 0.0451154)5.25588    

p = 101325 (0.9548846)5.25588    

p = 101325 * 0.78455659941

p = 79495.197 Pa

1 Pa = 9.86923267 * 10-6 atm

p= 784556.595340486 * 10-6 atm

p = 0.7845 atm

Nitrogen constitutes 79 %, so its partial pressure is 79 % of 0.7845 = 0.6197 atm

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