Finding the pH of the samples by using pH paper/universal indicator:
To find the pH of the following samples by using pH paper/universal indicator:
(i) Dilute Hydrochloric Acid
(ii) Dilute NaOH solution
(iii) Dilute Ethanoic Acid solution
(iv) Lemon juice
(vi) Dilute Hydrogen Carbonate solution
- Six test tubes
- Test tube stand
- Glass rod
- Measuring cylinder (10 mL)
- Standard pH colour chart
- pH paper
- Glass rod
- Universal indicator
- Samples of dilute HCl, dilute NaOH, dilute CH3COOH, lemon juice, Water, dilute NaHCO3
pH is the measure of hydrogen ion concentration to determine the alkalinity or acidity of a solution.
- If the pH value of a solution is less than 7 it is an acidic solution
- If the pH value of a solution is greater than 7 it is a basic solution
- If the pH value of a solution is equal to 7 it is a neutral solution
The pH scale consists of values which range from 0 (very acidic) to 14 (very alkaline). The numbers on the scale help to determine the hydrogen ion concentration.
- Wash six test tubes with distilled water and put them in test tube stand and label them as A, B, C, D, E, F.
- Take the given solutions in separate test tubes.
- Take glazed white tile, place 6 pH papers and label them A, B, C, D, E, F.
- Use a dropper or glass rod to put the respective sample solutions on the labelled pH paper placed on the white tile.
- Observe the colour change.
|S. No.||Sample Solution||Colour on pH paper||Approximate pH||Inference|
|F||Dil. NaHCO3||9||Turquoise (Light Blue)||Basic|
- The pH of dil. HCl, CH3COOH and lemon juice is less than 7 and therefore, they are acidic in nature.
- The pH of dil. NaOH and NaHCO3 is more than 7 and therefore, they are basic in nature.
- The pH of water is 7 and therefore, it is neutral.
- The acids and bases solution should be used with care.
- Use distilled water for preparing solutions.
- Use only standard colour charts for finding the pH value.
- Do not touch the pH paper with dirty and wet hands.
- Glass rod or dropper used for one sample should be washed thoroughly before using it for the other samples.