Studying the pH of Strong Acid, Weak Acid, Salt, and Buffer Solutions

1661 Words Oct 19th, 2014 7 Pages
Studying the pH of Strong Acid, Weak Acid, Salt, and Buffer Solutions
The purpose of the current experiment was to determine the pH of various hydrochloric acid and acetic acid solutions, to determine the pH of various salt solutions, to prepare a buffer solution, and determine the effects of adding a strong acid and strong base to the buffer solution versus adding a strong acid and strong base to water. The measured pHs for the hydrochloric acid solutions were 1.6, 2.2, 2.9, and 3.8. The measured pHs for the acetic acid solutions were 2.9, 3.9, 4.2, and 4.4. The pHs measured for the salts were 4.3 for sodium chloride, 7.3 for sodium acetate, 8.9 for sodium bicarbonate, 10.8 for sodium carbonate, 7.9 for ammonium chloride, and 6.9 for
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Theoretical pHs determined by taking (–log) of HCl concentration.
Table 2
Concentration of acetic acid (M) measured pH theoretical pH
1.0x10^-1 2.73 2.9
1.0x10^-2 3.08 3.4
1.0x10^-3 3.82 3.9
1.0x10^-4 4.65 4.4
Table 2: Measured pHs for various acetic acid solutions.
To determine the theoretical pH for each solution of acetic acid:
1.8x10-5 = [acetate] [H3O+]/[acetic acid] QUOTE
1.8x10-5 = [x][x]/[1.0x10-1] x= (1.0x10-1)(1.8x10-5) x = [H3O+] pH= -log[H3O+]

Table 3
Concentration of acetic acid (M) Calculated Ka theoretical Ka
1.0x10^-1 1.7x10^-5 1.8x10^-5
1.0x10^-2 1.7x10^-5 1.8x10^-5
1.0x10^-3 1.7x10^-5 1.8x10^-5
1.0x10^-4 1.7x10^-5 1.8x10^-5
Table 3: Calculated Ka values for each acetic acid solution.
To determine the experimental Ka values for each acetic acid solution:

For each solution of acetic acid, the respective [acetic acid] should be used.
Table 4
Salt Salt Type Measured pH
NaClneutral 6.65
NaC2H3O2 basic 7.00
NaHCO3 acid or base 8.72
Na2CO3 basic 10.50
NH4Cl acidic 5.96
NH4C2H3O2 acid or base 6.85
Table 4: Measured pHs and determined salt types for each of six salts in the procedure.
Table 5 solution measured pH theoretical [H3O+] calculated pH distilled water 6.88 1x10^-7 7 buffer solution 4.42

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