General Science Questions (MCQs) for Competitive Examinations
General Science Multiple choice questions for GK paper in SSC, NDA, CDS, UPSC, UPPSC and State PSC Examinations. These questions are part of GKToday’s 35000+ MCQs Bank Course in GKToday Android App
41. The smallest size of a cell that can be seen with naked eye is _____:
[A] 1 micron
[B] 10 micron
[C] 100 micron
[D] 1000 micron
Show Answer
Correct Answer: C [100 micron]
Notes:
The smallest objects that can be seen with unaided eye are about 0.1 mm long, which is equal to 100 micrometres. Micron (u) is an alternate name of micrometre.
42. Valency of an element depends on which of the following?
- Number of losing electrons
- Number of gaining electrons
- Number of sharing electrons
Select the correct answer from the codes given below:
[A] Only 1 and 2
[B] Only 1 and 3
[C] Only 2 and 3
[D] All of the above
Show Answer
Correct Answer: D [All of the above ]
Notes:
Valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. It is the number of electrons present in outermost orbit of that element and refers to the tendency to attain octet configuration. Atoms would react to attain an octet configuration, that is, stable configuration, by gaining, losing or sharing electrons.
43. Silicon is a:
[A] Semiconductor
[B] Insulator
[C] Nonconductor
[D] Conductor
Show Answer
Correct Answer: A [Semiconductor]
Notes:
Silicon is a chemical element with the symbol Si and atomic number 14. Over 90 percent of the Earth’s crust is composed of silicate minerals. Highly purified silicon is used in semiconductor electronics in manufacturing microships.
44. The gas causing acid rain in an industrial area is:
[A] Carbon dioxide
[B] Carbon monoxide
[C] Sulphur dioxide
[D] Methane
Show Answer
Correct Answer: C [Sulphur dioxide]
Notes:
The main gases responsible for causing acid rain are sulphur dioxide as well as nitrous oxides. The main sources of sulphur dioxide are metal working industries and coal-fired power stations whereas nitrous oxide is from vehicles and fuel combustion.
45. Phosphorus is kept in water because:
[A] its ignition temperature is very high
[B] its ignition temperature is very low
[C] its critical temperature is high
[D] its critical temperature is low
Show Answer
Correct Answer: B [its ignition temperature is very low]
Notes:
The allotropic form of Phosphorus (white phosphorus) is less stable and therefore highly reactive because of angular strain in P4 molecule where the angles are only 60o. Having very low ignition temperature, it readily catches fire in air to give dense white fumes of P4O10. So it is kept in water to avoid oxidation by the oxygen present in air.
46. Which of the following metal is most reactive?
[A] Potassium
[B] Calcium
[C] Sodium
[D] Zinc
Show Answer
Correct Answer: A [Potassium]
Notes:A reactive metal is one that readily reacts with other elements to give up its electrons. The order of intensity of reactivity is known as reactivity series. Potassium is at the top of the series and hence most reactive. Reactivity of some metals are given in descending order:
- K > Na > Ca > Mg > Al > Zn > Fe > Pb > Cu
47. Rock Salt contains which mineral?
[A] Gypsum
[B] Sodium
[C] Potassium
[D] Magnesium
Show Answer
Correct Answer: B [Sodium]
Notes:
Rock salt is the mineral (natural) form of sodium chloride (NaCl). It has high quantities of phosphorous, calcium, potassium, iron, magnesium, zinc, selenium, copper, bromine, zirconium and iodine. All of these minerals occur naturally.
48. Bhopal gas tragedy is associated with leakage of:
[A] carbon dioxide
[B] nitrogen dioxide
[C] sulphur dioxide
[D] methyl isocyanate
Show Answer
Correct Answer: D [methyl isocyanate]
Notes:
The Bhopal disaster, also referred to as the Bhopal gas tragedy, was a gas leak incident in India, considered one of the world’s worst industrial disasters. It occurred on the night of 2–3 December, 1984 at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal, Madhya Pradesh. Over 500,000 people were exposed to methyl isocyanate gas and other chemicals. The toxic MIC (Methyl isocyanate led to death of public on its way in and around the shanty towns located near the plant.
49. The acid which fails to liberate carbon dioxide from sodium bicarbonate is:
[A] Acetic acid
[B] Formic acid
[C] Carbonic acid
[D] Sulphuric acid
Show Answer
Correct Answer: D [Sulphuric acid]
Notes:Sodium bicarbonate and organic acid (Formic acid, Acetic acid, Carbonic acid, etc) react vigorously to liberate carbon dioxide. For example, Sodium bicarbonate (NaHCO3) when treated with acetic acid reacts vigorously to liberate carbon dioxide.
- NaHCO3 + CH3COOH —> CH3COONa + H2O + CO2
50. If the sewage is fully oxidized, the nitrogen is in the form of:
[A] Nitrites
[B] Ammonia
[C] Nitramines
[D] Nitrates
Show Answer
Correct Answer: D [Nitrates]
Notes:Oxidized forms of nitrogen include nitrite (NO2) and nitrate (NO3). Nitrogen mainly occurs in wastewater in this form. Because nitrite is easily oxidized to nitrate, nitrate is the compound predominantly found in groundwater and surface waters.
- 4NH4O —> 4NH4(+) + 4OH(–)
- 4OH(–) —> 2H2O + O2
- NH4 + O2 —> NO2(–) + 2H2O
- 2NO2(–) + O2 —> 2NO3(–)
