Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
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21. Which is the first element in the Actinoid series?
[A] Actinium
[B] Bohrium
[C] Mendelevium
[D] Nobelium
Show Answer
Correct Answer: A [Actinium]
Notes:
The actinoid series comprises of the 15 metallic chemical elements with atomic numbers from 89 to 103 starting from actinium through lawrencium.
22. Which of the following represents the cell potential?
[A] sum of the electrode potentials of the cathode and anode
[B] difference between the electrode potentials of the cathode and anode
[C] half of the sum of the electrode potentials of the cathode and anode
[D] twice the difference between the electrode potentials of the cathode and anode
Show Answer
Correct Answer: B [difference between the electrode potentials of the cathode and anode]
Notes:
The cell potential is the difference between the electrode potentials (reduction potentials) of the cathode and anode. It is measured in volts.
23. What is the S.I unit of Molar conductivity?
[A] S m3 mol-2
[B] S m2 mol-2
[C] S m-1 mol2
[D] S m2 mol-1
Show Answer
Correct Answer: D [S m2 mol-1]
Notes:
If conductivity(κ) of the solution is expressed in S m2 and the concentration(c) is expressed in mol m-3, then the units of Molar conductivity are expressed in S m2 mol-1.
24. What are the by-products of a hydrogen fuel cell?
[A] Water, heat and ozone
[B] Water and heat
[C] Water and ozone
[D] Heat, methane and Carbon dioxide
Show Answer
Correct Answer: B [Water and heat]
Notes:
The only by-products in a fuel cell by combining hydrogen and oxygen are water and heat. They do not emit greenhouse gases or other air pollutants.
25. What is the octane number of iso-octane?
[A] 1
[B] 0
[C] 100
[D] 200
Show Answer
Correct Answer: C [100]
Notes:
Octane number, also known as octane rating, are based on a scale on which iso-octane is 100, which means minimal knock, and heptane is 0. The higher the octane number, the more compression required for fuel ignition.
26. Which of these elements is added to Natural rubber in the process of vulcanisation?
[A] Carbon
[B] Sulphur
[C] Potassium
[D] Manganese
Show Answer
Correct Answer: B [Sulphur]
Notes:
Addition of sulphur to hot rubber cause changes that improve its physical properties in a spectacular manner. This process is called as vulcanization.
27. Which of these metals is commonly used in tanning of leather?
[A] Phosphorous
[B] Indium
[C] Manganese
[D] Chromium
Show Answer
Correct Answer: D [Chromium]
Notes:
Chromium(III) salts are used in the tanning of leather. Chromium is a steely-grey, lustrous, hard and brittle transition metal which is also used as an additive in stainless steel.
28. Which of the following is also used as a dry lubricant?
[A] Graphite
[B] Diamond
[C] Alpha sulphur
[D] Beta Sulphur
Show Answer
Correct Answer: A [ Graphite ]
Notes:
Graphite is also used as a dry lubricant. Dry lubricants are those materials that despite being in the solid phase, are able to reduce friction between two surfaces sliding against each other without the need for a liquid oil medium.
29. Which of the following metals is the first metal used by a man?
[A] Gold
[B] Copper
[C] Silver
[D] Iron
Show Answer
Correct Answer: B [Copper]
Notes:
A copper awl is the oldest metal object unearthed to date in the Middle East. The discovery reveals that metals were exchanged across hundreds of miles in this region more than 6,000 years ago, centuries earlier than previously thought, researchers say.
30. Most liquids that conduct electricity are solutions of acids, base and which of the following?
[A] Aluminium
[B] Copper
[C] Iron
[D] Salts
Show Answer
Correct Answer: D [Salts]
Notes:
Solutions that contain ions are good conductors of electricity, such as, acids, bases, salt water. Tap water, lemon juice and mercury is the best liquid conductor compare with others. Because of any solution to conduct, you need ions or free electrons.
