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Science · 2023 · 4 marks
CBSE 2023 · Region 2 · Set 1 · Q37
The teacher while conducting practicals in the laboratory divided the students into three groups and gave them various solutions to find out their pH…
The teacher while conducting practicals in the laboratory divided the students into three groups and gave them various solutions to find out their pH and classify them into acidic, basic and neutral solutions. Group A - Lemon juice, vinegar, colourless aerated drink Group B - Tomato juice, coffee, ginger juice Group C - Sodium hydroxide, sodium chloride, lime water
(a)
For the solutions provided, which group is/are likely to have pH value (i) less than $\displaystyle 7$, and (ii) greater than $\displaystyle 7$ ?
(b)
List two ways of determining pH of a solution
(c)
Explain, why the sour substances such as lemon juice are effective in cleaning the tarnished copper vessels.
OR
(c)
"pH has great importance in our daily life." Justify this statement by giving two examples.
Marking-scheme solution
(a)(i)
Groups A and B - less than $\displaystyle 7$
(ii)
Group C - greater than $\displaystyle 7$
(b)
pH paper and universal indicator.
(c)
Copper vessel is tarnished due to formation of basic copper oxide.
Lemon juice being acidic react with copper oxide and the salt formed is washed away.
OR
(c)
• An optimal pH is required for digestion.
Change in pH can cause tooth decay
Animals and plants defend themselves through change in pH .
Survival of aquatic life becomes difficult when pH of river water becomes low.
All Acids, Bases and Salts questions2023 question paperNCERT solutions: Acids, Bases and SaltsPractice Acids, Bases and Salts →
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CBSE Class 10 Science past-paper question from the 2023 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.