Question

Be sure to answer all parts. Chloroacetic acid, CICH,COOH, has a pK, of 2.87. What are [H3O+], pH, [CICH,C00-], and [CICH,COOH) in 2.25 M CICH,COOH? [H30+] = M [CICH,C00-] = [CICH,COOH)= pH=

Answer 1

The reaction, in this case, would look something like this:

+OH +-000'H10+ O'H + HOOD'HI

Now, since the initial concentration of the acid is given, we'll draw an ICE table:

	[ClCH2COOH]	[ClCH2COO-]	[H3O+]
Initial Concentration	2.25 M	0	0
Change in Concentration	-x	+x	+x
Equilibrium Concentration	(2.25 - x) M	x M	x M

Now, we have to ascertain the value of Ka from the given value of pKa

pk = -log(K)

2.87 = -log(K)

K, = 0.00135

Now, from the reaction, we can write the following relation:

(CICH,C00-][H30+1 CICH COOH

0.00135=925-

From this we will get the following quadratic equation:

0 = x + 0.001352 -0.00304

Solving this quadratic equation would give us the value of x, which is as follows:

= 0.0544

So, the equilibrium concentrations of all the species are as follows:

[H3O+] = 0.0544 M

[ClCH2COO-] = 0.0544 M

[ClCH2COOH] = 2.25 - 0.0544 = 2.20 M

Now, we'll ascertain the pH of the solution:

+of601- = Hd

pH = -log(0.0544

pH = 1.26