General Science Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination
21. Consider the following differences between Hard water and Soft water:
- While hard water has high calcium and magnesium content, soft water has high sodium content
- Hard water does not easily lather with soap, whereas soft water easily lather with soap
Which of the above statements is/are correct?
[A] 1 Only
[B] 2 Only
[C] Both 1 & 2
[D] Neither 1 nor 2
Show Answer
Correct Answer: C [ Both 1 & 2]
Notes:
Both are correct statements
Hard water is generally found in areas where groundwater is in contact with limestone, chalk and dolomite and gets higher amount of calcium and magnesium dissolved in it. Soft water is found in areas where groundwater usually travels through peat, igneous rock or sandstone sources, and does not contain as much calcium and magnesium. In fact, it contains higher amount of sodium ions.
22. Which of the following chemicals is also known as "Vitriol of clay”?
[A] Aluminium sulphate
[B] Sodium silicate
[C] Zinc sulphate
[D] Copper(II) sulphate
Show Answer
Correct Answer: A [ Aluminium sulphate]
Notes:
Aluminium sulphate is also known as Vitriol of clay. It is soluble in water and is mainly used as a flocculating agent in the purification of drinking water
23. Consider the following pairs:
- Red vitriol – Cobalt(II) sulphate heptahydrate
- Black vitriol – Aluminium sulphate
- Vitriol of Mars – Iron(III) sulphate
Which of the above is/are correct?
[A] 1 & 3 Only
[B] 2 Only
[C] 3 Only
[D] 1, 2 & 3
Show Answer
Correct Answer: A [ 1 & 3 Only]
Notes:
Black vitriol is a mixture of iron (II) sulphate and iron sulphide. Other two pairs are correct.
24. Consider the following statements:
- Addition of salt to pure water increases the boiling point of water and decreases the freezing point of water
- When methyl alcohol is added to water, boiling point of water decreases
Which of the above statements is/are correct?
[A] 1 Only
[B] 2 Only
[C] Both 1 & 2
[D] Neither 1 nor 2
Show Answer
Correct Answer: C [ Both 1 & 2]
Notes:
Both are correct statements
25. Which of the following is incorrect about the Inter atomic and Intermolecular Forces?
[A] Both the forces are electrical in origin
[B] Both the forces are active over short distances
[C] General shape of force-distance graph is similar for both the forces
[D] None of the above
Show Answer
Correct Answer: D [None of the above]
Notes:
Comparison between Inter atomic and Intermolecular Forces: (i) Both Inter atomic and Intermolecular forces are electrical in origin. (ii) Both Inter atomic and Intermolecular forces are active over short distances. (iii) General shape of force-distance graph for both the forces is similar. (iv) Both the forces are attractive up to certain distance between atoms/molecules and become repulsive when the distance between them becomes less than that value.
26. Which of the following is responsible for the anomalous behaviour of lithium in the periodic table?
[A] exceptionally small size of its atom and ion
[B] high polarising power
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
The anomalous behaviour of lithium is due to the : (i) exceptionally small size of its atom and ion, and (ii) high polarising power (i.e., charge/radius ratio).
27. What is the general electron configuration of all alkaline earth metals?
[A] ns1
[B] ns2
[C] ns2 np6
[D] None of the above
Show Answer
Correct Answer: B [ns2]
Notes:
The general electron configuration of all alkaline earth metals is ns2.
28. Which of the following is NOT correct about Alkynes?
[A] They contain at least two triple bond between two carbon atoms
[B] The number of hydrogen atoms is less in alkynes as compared to alkenes
[C] The general formula of Alkynes is CnH2n–2
[D] All are correct
Show Answer
Correct Answer: A [They contain at least two triple bond between two carbon atoms]
Notes:
Alkynes contain at least one triple bond between two carbon atoms. The number of hydrogen atoms is less in alkynes as compared to alkenes or alkanes. Their general formula is CnH2n–2.
29. Which of the following is correct about Hard water?
[A] it is free from soluble salts of calcium and magnesium
[B] it does not give lather with soap
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: B [it does not give lather with soap]
Notes:
Presence of calcium and magnesium salts in the form of hydrogencarbonate, chloride and sulphate in water makes water ‘hard’. Hard water does not give lather with soap.
30. Which of the following elements have a compound named as Hydrogen peroxide?
[A] Hydrogen, Carbon and Oxygen
[B] Hydrogen only
[C] Hydrogen and Oxygen
[D] Hydrogen, Oxygen and Potassium
Show Answer
Correct Answer: C [Hydrogen and Oxygen]
Notes:
Hydrogen peroxide is a compound of Hydrogen and Oxygen.
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