Class 11 Chemistry · Chapter 16 · Test 1
Lab Safety and Skills
This test covers General Lab Instructions, Types of Hazards, Waste Disposal, First Aid, Acid-Base Titration, and the Identification of Anions and Cations (Basic Radicals).
37 questions · 25 min · 37 marks
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Sample questions
The first 5 of 37. Try each one, then tap to see the answer.
Question 1
While taking a reading with a burette, why is it always advisable to read the lower meniscus for the colorless liquids and the upper meniscus for the coloured liquids?
- Abecause it is more convenient
- Bbecause colorless liquids have more surface tension than colored liquids
- Cbecause lower meniscus does not exist for colored liquids
- Dbecause of the parallax effect
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Answer: D
Burette readings are affected by the parallax effect, which is why an anti-parallax card or white paper is used when noting readings.
Question 2
Why is phenolphthalein indicator more appropriate to use during the titrations which involve a strong acid and a strong base?
- Abecause it is itself weakly acidic
- Bbecause the pH at the equivalence point as well as the pH over which the colour of phenolphthalein changes match each other
- Cbecause the solution at the end of titration is acidic
- Dbecause the solution at the end of titration is basic
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Answer: B
An indicator is suitable when its colour change range matches the pH at the equivalence point of the reaction.
Question 3
Which cation gives a white gelatinous precipitate upon the addition of aqueous ammonia?
- ACr3+
- BCr2+
- CZn2+
- DAl3+
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Answer: D
Al3+ gives a white gelatinous precipitate; Cr3+ gives a green precipitate, and Zn2+ gives a white precipitate that dissolves in excess ammonia.
Question 4
Addition of NH4OH to an aqueous solution of a cation gives a green precipitate which turns brown upon standing. Which basic radical is indicated?
- ACu2+
- BCr3+
- CFe2+
- DFe3+
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Answer: C
Fe2+ gives a green precipitate of Fe(OH)2 which changes to an orange-brown precipitate on standing due to oxidation.
Question 5
On dry heating test for salt analysis, the evolution of a colorless, odorless gas that turns lime water milky suggests the presence of:
- AChloride ion (Cl-)
- BSulfate ion (SO4 2-)
- CCarbonate ion (CO3 2-)
- DNitrate ion (NO3-)
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Answer: C
A carbonate evolves CO2 gas which turns lime water milky.
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