The teacher while conducting practicals in the laboratory divided the students into three groups and gave…
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 7, and (ii) greater than 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.
Solution
(a) (i) Groups A and B – less than 7
(ii) Group C – greater than 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.