# Pre Calculs

posted by
**Erica**
.

The pH of a chemical solution is given by the formula pH = -log10 [H+] where [H+] is the concentration of hydrogen ions in moles per liter. Values of pH range from 0 (acidic) to 14 (alkaline).

(a) what is the pH of the solution for which [H+] is 0.1?

(b) What happens to pH as the hydrogen ion concentration decreases?

(c)Determine the hydrogen ion concentration of an orange pH =3.8

(d) Determine the hydrogen ion concentration of human blood pH =7.4

All of these are simple log questions.

Are you having trouble with logs? For example, the answer to part (a) is just the -log(0.1).

I am. These are all log questions. And I think the main problem is how to put the question into my calculator. I am struggling the logs . Our teacher doesn't seem to teach things to our level.

For (a) use H+ = .01 in the formula to get

pH=-log10[.1] = -log10[10^-1]

For (b) you should see that the - sign before the log tells us the pH and H+ are inversely related.

For (c) set pH=3.8 in the formula and solve for H+

3.8=-log10[H+]

and for (d) 7.4=-log10[H+], so solve for H+.