✓ Board-verified
Science · 2023 · 3 marks
CBSE 2023 · Region 5 · Set 1 · Q28
(a)Sometimes the pH of our mouth gets lower than $\displaystyle 5 \cdot 5$. Why ?(b)A basic salt 'X' is obtained by heating baking soda followed by crystallisation. Identify 'X' and state its two industrial uses.(c)Why do copper sulphate crystals turn white on heating ?
(a)
Sometimes the pH of our mouth gets lower than $\displaystyle 5 \cdot 5$. Why ?
(b)
A basic salt 'X' is obtained by heating baking soda followed by crystallisation. Identify 'X' and state its two industrial uses.
(c)
Why do copper sulphate crystals turn white on heating ?
Marking-scheme solution
(a)
Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth after eating.
(b)
$\displaystyle \mathrm{X}: \mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O} /$ Washing soda /
Sodium carbonate decahydrate
Uses :
Glass, soap and paper industries
Manufacture of borax
Cleaning agent
Removing permanent hardness of water
(c)
The water of crystallisation is removed./
\[\mathrm{CuSO}_{4.5 \mathrm{H}_{2} \mathrm{O}} \xrightarrow{\text { heat }} \underset{\text { (white) }}{\mathrm{CuSO}_{4}}+5 \mathrm{H}_{2} \mathrm{O} \uparrow
\]
More from Acids, Bases and Salts
- Assertion: Concentrated nitric acid is diluted by adding water slowly to acid with constant stirring. Reason…2025 · asked 3×
- An aqueous solution turns red litmus blue. Excess addition of which of the following solution would reverse…2026 · asked 3×
- (i) A compound 'X' which is prepared from gypsum has the property of hardening when mixed with proper…2023 · asked 3×
- Which of the given option represents a family of salts?2025 · asked 3×
- Select a pair of natural indicator from the following:2024 · asked 3×
- In order to prepare dry hydrogen chloride gas in humid atmosphere the gas produced is passed through a guard…2025 · asked 3×
- Acid-base indicators can be used to distinguish between an acid and a base. Universal indicator, a mixture of…2025 · asked 3×
- Consider the following reactions: (i) Dilute hydrochloric acid reacts with sodium hydroxide. (ii) Magnesium…2025 · asked 3×
CBSE Class 10 Science past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.