Practice Problems for pH
Agronomy 354

1. If the H+ concentration is 0.0001 M/l, what is the pH?

2.  If the H+ concentration is 0.00001 M/l, what is the OH- concentration? 3. If the H+ concentration is 0.00005 M/l, what is the pH?

4. If the pH is 4.5, what is the pOH?

pH + pOH = 14
pOH = 14 - 4.5 = 9.5

pOH = 9.5

5. If a soil has a pH of 4.7, what is the H+ concentration of the soil solution?

6.  If a CEC is 20 meq/100 g soil and analyses find 12 meq Ca/100 g, 2 meq K/100 g, 1 meq Mg/100 g, 1 meq Na/100 g, 0.5 meq H/100 g, and 3.5 meq Al/100 g, what is the percentage base saturation?

%BS = meq basic ions/CEC

Basic ions = Ca, Mg, K, NA; Acidic ions = H and Al

 meq BS = 12 + 2 + 1 + 1 = 16 meq/100 g soil

CEC = 12 + 2 + 1 + 1 + 0.5 + 3.5 = 20 meq /100 g soil

%BS =  16/20 = 80%

7. Recall that a 90% base saturation in a Midwest soil approximately equals a pH of 6.5. Therefore, this soil's pH would be lower; perhaps 5.8 or so. You may verify this by checking the graph given in lecture that relates pH and % base saturation for various soil components.


Return to:
 354 Course Syllabus
Loynachan 354 Homepage