1) To calculate the pH of a weak acid. I know the concentration of the acid and
ID: 845606 • Letter: 1
Question
1) To calculate the pH of a weak acid. I know the concentration of the acid and its conjugate base, the volume of the solution, and the temperature ( 30 degrees celsius). what else do I need to know? explain and show work
a) The kd for H+ of the acid
b) I have all the necessary information
c) The total H+ concnetration (i.e. free and bound to the acid)
d) the pKa of the acid
e) The free-energy change for release of the H+
2) What is the pH of a solution containing 0.2 M acetic acid (pKa = 4.7) and 0.1 M sodium acetate ( the conjugate base of acetic acid) ? show work
3) If 20g of NaOH are dissolved in 1000mL of pure water, what pH should be expected?
Explanation / Answer
1) pKa of acid
2) pH = pKa + log[salt]/[acid]
= 4.4 + log 0.1 / 0.2 = 4.4-0.303 =4.09
3) pOH = - log [OH]
20/40 mol in 1000ml = 0.5M
-log 0.5 = 0.30
pH = 14-pOH = 14- 0.30 = 13.69
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