CBSE 2025 · Region 2 · Set 1 · Q37 · 4 marks
Acid-base indicators can be used to distinguish between an acid and a base. Universal indicator, a mixture of several indicators, shows different colours at different concentrations of acids and bases, thereby indicating their pH on the pH scale of $\displaystyle 0-14$. The pH of a solution is measured by pH paper, which is a paper impregnated with a universal indicator.
Answer the following questions :(a)Solution P is a strong acid while solution Q is a strong base. On the pH scale, where would you place the solutions P and Q ?(b)A solution has a pH of 7. Name a compound you would use to(i)increase its pH , and (ii) decrease its pH.(c)When the pH of a solution is decreased from $\displaystyle 4$ to $\displaystyle 2$, what effect does it produce on its hydronium ion concentration ? State the colour change shown by the pH paper.(ii)A person is feeling pain and irritation in the stomach due to indigestion. What could be the pH of the fluid in the stomach ? Write the common name of the medicines people use for remedy. Give the chemical name of "milk of magnesia" often used for this purpose.
Acid-base indicators can be used to distinguish between an acid and a base. Universal indicator, a mixture of several indicators, shows different colours at different concentrations of acids and bases, thereby indicating their pH on the pH scale of $\displaystyle 0-14$. The pH of a solution is measured by pH paper, which is a paper impregnated with a universal indicator.
Answer the following questions :
(a)
Solution P is a strong acid while solution Q is a strong base. On the pH scale, where would you place the solutions P and Q ?
(b)
A solution has a pH of 7. Name a compound you would use to
(i)
increase its pH , and (ii) decrease its pH.
(c)
When the pH of a solution is decreased from $\displaystyle 4$ to $\displaystyle 2$, what effect does it produce on its hydronium ion concentration ? State the colour change shown by the pH paper.
(ii)
A person is feeling pain and irritation in the stomach due to indigestion. What could be the pH of the fluid in the stomach ? Write the common name of the medicines people use for remedy. Give the chemical name of "milk of magnesia" often used for this purpose.
Marking-scheme solution
(a) P - pH $\displaystyle 0$ to $\displaystyle 4$ \(\displaystyle \mathrm{Q}-\mathrm{pH} 12\) to $\displaystyle 14$
(b) (i) By adding sodium hydroxide
(ii) By adding hydrochloric acid
(c)
Acids, Bases and SaltspH Scale and its Importance in Everyday LifeUnderstandcase_studymedium
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CBSE Class 10 Science past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.