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
31. Which of the following is correct about HCl gas?
[A] It is a colourless and pungent smelling gas
[B] It is extremely soluble in water
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
It is a colourless and pungent smelling gas. It is easily liquefied to a colourless liquid and freezes to a white crystalline solid . It is extremely soluble in water.
32. Which of the following is NOT correct about Ethanol?
[A] It is a good solvent
[B] It gives out hydrogen when reacted with Sodium
[C] It is an odorless liquid
[D] All are correct
Show Answer
Correct Answer: C [It is an odorless liquid]
Notes:
Ethanol is a good solvent and reacts with sodium leading to the evolution of hydrogen. It is a colorless liquid with a slight characteristic odor.
33. What is an alloy of mercury with some other metal generally known as?
[A] Galinston
[B] Amalgam
[C] Megalium
[D] Yellow metal
Show Answer
Correct Answer: B [Amalgam]
Notes:
Amalgam is the general name given to an alloy of mercury with some other metal. It can be a solid, liquid or a soft paste depending on the composition of the constituents.
34. Bayer process is related to which of the following?
[A] production of Copper oxide
[B] production of Alumina
[C] production of Zinc oxide
[D] production of Silicon dioxide
Show Answer
Correct Answer: B [production of Alumina]
Notes:
The Bayer process is the industrial process of refining bauxite to produce alumina (aluminium oxide). In this process, Alumina is separated from the bauxite ore by using a hot solution of caustic soda (sodium hydroxide) and lime (calcium oxide).
35. Which of the following is correct about the principal quantum number?
[A] It determines the size of the orbital
[B] It can have positive integer values
[C] It identifies the shell
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Principal quantum number determines the size and to a large extent the energy of the orbital. It can have positive integer values of 1, 2, 3 and so on. It also identifies the shell.
36. What is the total number of allowed orbitals in a shell, if principal quantum number is n?
Show Answer
Correct Answer: C [n2]
Notes:
The principal quantum number also helps in identifying the shell. As the value of ‘n’ increases, the number of allowed orbital increases and are given by n2.
37. Which of the following quantum numbers is not necessary to identify an orbital?
[A] Principal quantum number
[B] Azimuthal quantum number
[C] Magnetic quantum number
[D] Electron Spin quantum number
Show Answer
Correct Answer: D [Electron Spin quantum number]
Notes:
An orbital is identified by the set of 3 quantum numbers: Principal quantum number, Azimuthal quantum number and magnetic quantum number.
38. Which of the following are the limitations of Bohr’s model of atom?
[A] it cannot explain spectrum of atoms containing more than one electron
[B] it cannot explain the Zeeman effect
[C] it cannot explain the Stark effect
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Bohr’s model of atom cannot explain spectrum of atoms containing more than one electron. Also, it cannot explain the Zeeman effect i.e. splitting of spectral line in presence of magnetic field. It also fails to explain Stark effect i.e. splitting of spectral line in presence of electric field.
39. Which of the following substance was used as a moderator in CIRUS reactor?
[A] Heavy water
[B] water
[C] solid graphite
[D] No moderator was used
Show Answer
Correct Answer: A [Heavy water]
Notes:
CIRUS (Canada India Research U.S.) reactor was constructed in 1960. This 40 MW reactor used natural uranium as fuel and heavy water as moderator.
40. Which of the following alpha-emitter is commonly used in smoke detectors?
[A] Bismuth – 209
[B] Amrecium-231
[C] Uranium-238
[D] Protactinium-231
Show Answer
Correct Answer: B [Amrecium-231]
Notes:
Americium-241 is an isotope of americium. It is the most common isotope of americium having a half-life of 432.2 years. It is radioactive and is commonly used in ionization type smoke detectors.
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