CBSE Class 10 Science 2019 · Paper 31/2/1 · Question 22(a)

Acids, Bases and Salts 2 marks Medium

A teacher provided acetic acid, water, lemon juice, aqueous solution of sodium hydrogen carbonate and sodium hydroxide to students in the school laboratory to determine the pH values of these substances using pH papers. One of the students reported the pH values of the given substances as 3, 12, 4, 8 and 14 respectively. Which one of these values is not correct ? Write its correct value stating the reason.

Answer

The pH of water is wrong: the correct value is $7$ , as water is neutral.

The value

12

reported for water is not correct. Correct value:

7

. Reason: water is neutral - neither acidic nor basic - because it contains equal amounts of

H^{+}

and

OH^{-}

ions; a pH of

12

would mean a strongly basic solution. (The other values fit: acetic acid

3

and lemon juice

4

are acidic, sodium hydrogen carbonate solution

8

is mildly basic and sodium hydroxide

14

is strongly basic.)

🔒 Step-by-step solution

CBSE Class 10 Science 2019 · Paper 31/2/1 · Question 22(a)

Answer

From the board papers

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