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Aim- To find the pH of different soap samples:i. Santoorii. Fiama di willsiii. Breezeiv. Keto soapv. Dovevi. LuxApparatus Required- A beaker, a dropper, pH paper distilled water, given samples, white glazed tile, etc. Principle- The hydronium (or hydrogen) ion concentration of a solution can be conveniently expressed in terms of pH. The pH of a solution is defined as the negative logarithm (base10) of hydronium (or hydrogen) ion concentration.

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The pH generally extends from 0 to 14.

The approximate pH of a given solution can easily be obtained by using wide range pH paper or universal indicator. The colour developed is matched with the colour in the colour chart and corresponding pH value noted.

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Colour chart with corresponding pH value

Ques. What is a pH paper?A pH paper is a strip of paper which after dipping in a solution of various indicator, has been dried up. When it is dipped in a given solution, it changes its colour. The shade of formed is compared to the chart provided for this purpose from which approximate pH can be found out. The pH papers are available in strips CHEMISTRY Page 3

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of 20-25 in the form of a small booklet. Its cover contains the chart of color for comparison.

pH paper bookletProcedure- i. Take soap and peel off small shaving of soaps

and dissolved it in into water.ii. Tear a small portion (1-2 cm) of pH paper with

clean and dry hands and place it on a white glazed tile.

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iii. Using a dropper transfer 1 to 2 drops of the first sample of the soap on the universal indicator paper (pH paper).

iv. Observe the colour developed on the pH paper and compare it with the colour in the colour chart on the cover of pH paper booklet.

v. Note the pH given against the colour which tallies with the colour developed on the pH paper.

vi. Repeat the procedure given above, for the other samples and note your observations.

Correct use of pH paper with dropper

S.NO. SAMPLES TAKEN pH OF THE SAMPLE

1 Santoor 9CHEMISTRY Page 5

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2 Fiama di wills 83 Breeze 94 Keto soap 95 Dove 76 Lux 9

Observation -

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Result- Acidic samples are: - None Neutral sample is: - Dove

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Basic sample are: - Santoor, Breeze, Keto soap, Lux

Precautions- i. Wash the test tube thoroughly with

distilled water, before use.ii. Use clean and dry hands to tear a pH

paper.iii. Wash the dropper thoroughly after

testing each sample.iv. Clean and dry the glazed tile before use.v. All solutions should be freshly prepared.

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