What is the pH of the resulting solution?

20.0 mL of pure HC2H3O2 is diluted to 1.30 L with water. The density of pure HC2H3O2 is 1.05 g/mL.

1 Answer
Dave
Apr 7, 2018

See Below

Explanation:

First we are gonna get mL of Acetic Acid into grams. Then get it into moles. Then get it into molarity. Then use the #K_A# for acetic acid to determine #[H^+]#, then pH.

20.0mL of #CH_3COOH xx 1.05g/"mL"# =
21g #CH_3COOH#
21g #CH_3COOH xx ("1mole"/"60.5g") = 0.347 "moles" CH_3COOH#

#(0.347 "moles" CH_3COOH)/(1.3 "liters")# = 0.267M #CH_3COOH#

#CH_3COOH K_A = 1.8xx10^-5#

#CH_3COOH = CH_3COO^- + H^+#

Using an ICE table (and assuming x << 0.267M)

#K_A = 1.85xx10^-5 = x^2/0.267#

x = 0.0022M = #[H^+]#
#pH = -log[H^+]#
#pH = -log(0.0022M)#
#pH = 2.66#

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