Problem

The structural formula for acetic acid is shown in Table Replacing hydrogen atoms on the c...

The structural formula for acetic acid is shown in Table Replacing hydrogen atoms on the carbon with chlorine atoms causes an increase in acidity, as follows:

Acid	Formula	Ka(25 °C)
Acetic	CH3COOH	1.8 × 10-5
Chloroacetic	CH2ClCOOH	1.4 × 10-3
Dichloroacetic	CHCl2COOH	3.3 × 10-2
Trichloroacetic	CCl3COOH	2 × 10-1

Using Lewis structures as the basis of your discussion, explain the observed trend in acidities in the series. Calculate the pH of a 0.010 M solution of each acid.

Table Some Weak Acids in Water at 25°c

Acid	Structural Formula*	Conjugate Base	Ka
Chlorous (HClO2)	H- O- Cl- O	ClO2-	1.0 × 10-2
Hydrofluoric (HF)	H-F	F-	6.8 × 10-4
Nitrous (HNO2)	H- O- N= O	NO2-	4.5 × 10-4
Benzoic (C6H5COOH)		C6H5COO-	6.3 × 10-5
Acetic (CH3COOH)		CH3COO-	1.8 × 10-5
Hypochlorous (HOCl)	H- O- Cl	OCl-	3.0 × 10-8
Hydrocyanic (HCN)	H -C ≡N	CN-	4.9 × 10-10
Phenol (HOC6H5)		C6H5O-	1.3 × 10-10