VSAQ for Ch 2 Acids, Bases and Salts Class 10 Science NCERT
Important Questions1
Name the acid present in ant sting.
Answer
Formic acid (Methanoic acid), HCOOH.
VSAQ
2
Which has higher concentration of H+ ions?
1 M HCl or 1 M CH3COOH.
Answer
1 M HCl has a higher concentration of H+ ions because when HCl dissolves in water it dissociates completely into ions while CH3COOH is a weak acid and does not dissociate into ions completely.
VSAQ
3
Why does tooth decay start when the pH of mouth is lower than 5.5?
Answer
At lower pH below 5.5, the calcium phosphate of enamel of tooth gets corroded, which leads to tooth decay.
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4
Fresh milk has a pH of 6. When it changes into curd (Yogurt), will its pH value increases or decreases? Why?
Answer
Curd contains lactic acid, so H+ ion concentration increases and thus pH will decrease. When milk changes into curd, its pH will decrease. Because curd contains lactic acid, so H+ ion concentration increases and thus pH will decrease.
VSAQ
5
Which is a stronger acid, with pH = 5 or with pH = 2?
Answer
pH = 2 (lower the pH, stronger the acid).
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6
Which gas is usually liberated when an acid reacts with a metal?
Answer
Hydrogen gas.
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7
How chloride of lime differs from calcium chloride?
Answer
CaOCl2 is the chloride of lime whereas CaCl2 is calcium chloride.
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8
Name a salt which does not contain water of crystallization.
Answer
Baking soda
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9
Three acidic solutions A, B and C have pH = 0, 3 and 5 respectively.
(a) Which solution has the highest concentration of H+ ions?
(b) Which solution has the lowest concentration of H+ ions?
Answer
(a) The solution with pH = 0 has highest concentration of H+ ions.
(b) The solution with pH = 0 has lowest concentration of H+ ions.
VSAQ
10
Dry HCl gas does not change the colour of dry blue litmus. Give reason to justify it.
Answer
Dry HCl (g) does not form ions, therefore it does not affect dry blue litmus.
VSAQ
11
Which is stronger acid, with pH = 5 or with pH = 2?
Answer
The acids with pH = 2 is stronger acid.
Greater pH value- more basic
Less pH value- more acidic
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12
What would be the colour of litmus in a solution of sodium carbonate?
Answer
The colour of litmus in a solution of sodium carbonate is blue.
VSAQ
13
What is meant by p and H in pH?
Answer
p stands for ‘protenz’ in German meaning power, H stands for hydrogen.
VSAQ
14
At what pH rain water is said to be acidic?
Answer
When pH < 5.5, the rain water becomes acidic.
VSAQ