Question 1: The molar concentration of OH– ions in a certain solution is 1.04 x 10-5 mol L-1. Calculate the pOH and then the pH of the solution.
Question 2: Death occurs if the pH of human blood plasma changes by more than about ±0.4 from its normal value of about pH = 7.4, the “safe” range is from neutral to slightly alkaline. What is the corresponding range of molar concentrations of hydrogen ions for which human life can be sustained?
Solution 1:
[OH–] = 1.04 x 10-5 mol L-1
pOH = – log 10 (1.04 x 10-5) = 4.98
pH + pOH = 14.00
pH = 14.00 – 4.98 = 9.02
Solution 2:
| Maximum pH = 7.8 | 7.8 = -log10[H+]max | [H+]max = 10-7.8 |
| Maximum pH = 7.0 | 7.0 = -log10[H+]max | [H+]max = 10-7.0 |
From the definition of a logarithm we have [H+] = 10-7.8 . The easiest way of solving this on your calculator is to use “shift-log” (which is 10x) then type —7.8 then equals. Take care to use “shift-log” = 10x not “shift-In” = ex.
[H +]MAX = 1.58 x 10-8 mol L-1
[H +]MIN = 1.00 x 10-7 mol L-1
Human blood covers only a small range of proton concentrations. Here all explanation based on Acid Base Equilibrium.
