The dissolution of common salt in water is a physical change because
the salt can be obtained by crystallization
the salt can be recovered by the evaporation of water
heat is not generated during mixing
the solution will not boil at 100oC
Correct answer is B
The evaporation of water is a physical change. When water evaporates, it changes from the liquid state to the gas state, but it is still water; it has not changed into any other substance.
From the above diagram; The caustic soda in the conical flask serves to
dry ethene gas
remove carbon (iv) oxides from ethene
remove carbon (ii) oxide from ethene
remove sulphur (iv) oxide from ethene
Correct answer is B
Caustic soda, \(NaOH\) , serves to remove gaseous impurities from the gas evolved during the laboratory preparation of ethene. Basically, the major impurities are Sulphur (IV) oxide and Carbon (IV) oxide.
CH3COOH
CH3COOCH3
CH3COOC2H5
C2H5COOCH3
Correct answer is A
No explanation has been provided for this answer.
Clothes should be properly rinsed with water after bleaching because
the bleach decolourizes the clothes
chlorine reacts with fabrics during bleaching
the clothes are sterilized during bleaching
hydrogen chloride solution is produced during bleaching
Correct answer is D
No explanation has been provided for this answer.
Which of these metals CANNOT replace hydrogen from alkaline solutions?
Aluminium
Zinc
Tin
Iron
Correct answer is D
Aluminum, Zinc, and Tin react with both acids and alkalis to liberate hydrogen and so all are amphoteric metals except iron.
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