The pH describes the degree of acidity and alkalinity of an aqueous solution, expressed as pH (not as PH value).
In the case of thermodynamic standard conditions, the aqueous solution with pH=7 is neutral, the pH is <7, and the pH>7 is alkaline.
There are many ways to measure the pH of a solution:
A pH indicator is added to the solution to be tested, and different indicators change color depending on different pH values.
E.g:
(1) If the acidic solution is dropped into the litmus test solution, the litmus test solution will turn red; when the alkaline solution is dropped into the litmus test solution, the litmus test solution will turn blue (the litmus test solution encounters the neutral liquid) Does not change color). The range of pH can be determined based on the investigation of the indicator.
(2) The leuco phenolphthalein solution is dropped into an acidic or neutral solution, and the color does not change; the leuco phenolphthalein solution is dropped into the alkaline solution, and the solution turns red.
Note: When adding the ph indicator to the colored test solution, choose a ph indicator that produces a significant color difference.
The titration can be used to make accurate pH standards.
Using pH test paper, pH test paper has a wide range of test papers and precision test papers. Use a glass rod to pry a little test solution onto the test paper. Then, according to the color change of the test paper and the color chart, the pH value of the solution can also be obtained. The table above is equivalent to a color chart.
Using a pH meter, a pH meter is an instrument that measures the pH of a solution by measuring the pH of the solution through a pH selective electrode such as a glass electrode. The pH meter can be accurate to two decimal places.
