Know the pH scale. The pH scale is usually presented from 0 to 14. The lower the number, the more acidic the solution. The higher the number, the more basic the solution. For example, orange juice would have a pH of 2 because it is quite acidic. In contrast, bleach has a pH of 12 as it is quite basic. Numbers in the middle of the scale are neutral, such as water, with a pH of 7. One level of pH is a 10x difference. For example, when comparing pH 7 to pH 6, pH 6 is ten times more acidic than pH 7. Furthermore, pH 6 would be 100 times more acidic than pH 8.
The equation can sometimes be seen as pH = -log10[H+]. Know that whether the equation has H3O+ or H+, they are the same. It is not vital to have a firm understanding of what a negative log is to calculate pH. Most calculators used at high school and post secondary level will have a log button.
In chemistry, square brackets usually indicate “concentration of”. So the equation of pH would be read as “pH equals the negative logarithm of the concentration of hydronium ions”.
For example, if the concentration is 1. 05 x 10-5 M, write the pH equation as: pH = -log10(1. 05 x 10-5 M)
For example, pH = -log10[H3O+] will mold into [H3O+] = 10-pH. pH can then be filled in as 10. 1
For example, take a pH value of 10. 1. Key in “10” followed by “EXP. ” Now key in “-/+” to have our value be negative. Finally, key in the pH of “10. 1”. Hit solve. You should get about 7. 943ᴇ-11, or 7. 94310-11. This means our concentration is 7. 94310-11 M.
