Instructions
- This tool generates a set of pH, pOH, and concentration values.
- To use the tool, specify a pH range (from-to values), a pH increment (∆pH), and a pkw value.
- You can change the default number of decimal places, if you want to.
What is computed?
- pH and pOH values are converted to concentration values, where
pH + pOH = pkw
[H+] = 10-pH
[OH-] = 10-pOH
kw = 10-pkw
- If the solvent is pure water at 25 degree Celsius, pkw = 14
- For other temperatures or solvents, pkw = 14 must be replaced with the correct value.
Indicators and their pH-color ranges
- A pH indicator is a substance that changes color in different pH environments. A universal indicator is a mixture of pH indicators that form a continuous spectrum of colors at different pH values. The most common indicators are
- Methyl Red
0714
Red at pH < 4.4. Yellow at pH > 6.2.
- Bromothymol blue
0714
Yellow at pH < 6. Blue at pH > 7.6.
- Phenolphthalein
0714
Orange at pH < 0. Colorless at pH 0 to 8.2. Fuschia at pH 8.2 to 12. Colorless at pH > 13.
- Thymol blue
0714
Red at pH < 1.4. Yellow at pH > 2.8 and pH < 8. Blue at pH > 9.6.
- Universal Indicator
0714
Red at low pH. Green at neutral pH. Blue-violet at high pH.
pH of common substances and materials
pH of Common Supplies and Biological Materials at 25 oC
from
▾▴ |
to
▾▴ |
example
▾▴ |
| 0 | 1 | battery acid |
| 1 | 3 | toilet bowl cleaner |
| 1 | 3 | human gastric content |
| 2 | 3 | lemon juice, vinegar |
| 2 | 4 | soft drinks |
| 2.5 | 3 | grapefruit juice, soda, tomato juice |
| 3 | 4 | orange juice |
| 4.5 | 5 | lysosomes |
| 4.6 | 8.4 | human feces |
| 4.8 | 8.2 | human duodenal content |
| 5 | 5.3 | black coffee |
| 5.5 | 5.5 | granules of chromaffin cells, human skin |
| 4.8 | 8.4 | human urine |
| 6.5 | 8 | drinking water |
| 6.5 | 7.5 | human saliva |
| 6.6 | 7.6 | human milk |
| 6.8 | 7 | human bile |
| 7.0 | 7.0 | pure water |
| 7.2 | 7.4 | cytosol |
| 7.3 | 7.5 | human spinal fluid |
| 7.35 | 7.45 | human blood |
| 7.5 | 7.8 | mitochondrial matrix |
| 7.5 | 8.4 | sea water |
| 7 | 8 | mild dish soap |
| 8 | 9.5 | baking soda |
| 8.1 | 8.1 | pancreas secretions |
| 9 | 10 | normal soap |
| 9 | 10 | borax |
| 10.5 | 12 | ammonia solution |
| 11 | 13 | tub and tile cleaner |
| 11 | 13.5 | oven cleaner, bleach |
| 13.5 | 14 | liquid drain cleaner |
Exercises
- Universal indicators are combinations of indicators typically with water and propan-1-ol as solvents. NaOH is added to adjust the pH of the combination. Why?
- The main components of a universal indicator are methyl red, bromothymol blue, phenolphthalein, and thymol blue. Why?
- An indicator mixture consists of bromothymol blue and thymol blue. What would be its color around pH = 7?
- What is the pH of pure water at 100 oC? Why?
References
Feedback
Contact us for any suggestion or question regarding this tool.
