Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. Which of the following is an alkaline earth metal?
[A] Pottasium
[B] Lead
[C] Copper
[D] Calcium
Show Answer
Correct Answer: D [Calcium ]
Notes:
The six elements in column 2 of the Periodic table are called Alkaline Earth Metals. These include Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba), and Radium (Ra).
2. What happens to the weight of Iron, when it rusts?
[A] Increases for long time
[B] Decreases then increases
[C] Increases then decreases
[D] Remains the same
Show Answer
Correct Answer: C [Increases then decreases]
Notes:
When iron or any other metal oxidizes, oxygen from the air combines with the iron to make iron oxide or rust. So, weight of the bar increases, due to the increased weight of oxygen which has combined with the iron. over time, the weight of the iron bar will tend to decrease, due to factors related more to erosion than to chemistry.
3. Who among the following had given the Atomic Theory?
[A] Benzamin Franklin
[B] Madam curie
[C] Albert Einstien
[D] John Dalton
Show Answer
Correct Answer: D [John Dalton]
Notes:
The correct answer is John Dalton. He proposed the Atomic Theory in the early 19th century, stating that matter is composed of indivisible atoms, each with a specific weight. Dalton’s work laid the foundation for modern chemistry. Notably, he also introduced the concept of atomic weights and was the first to use symbols to represent atoms of different elements.
4. Galena & Litharge are ores of which of the following metals?
[A] Mercury
[B] Zinc
[C] Copper
[D] Lead
Show Answer
Correct Answer: D [Lead]
Notes:
Galena and litharge are ores of lead. Galena is the most common ore of lead. It is the natural mineral form of lead (II) sulphid. Litharge is a secondary mineral that forms from the oxidation of galena ores. It is one of the natural mineral forms of Lead(II) oxide.
5. According to Avogadro’s hypothesis, equal volumes of gases contain equal number of?
[A] Atoms
[B] Molecules
[C] Particles
[D] Electrons
Show Answer
Correct Answer: B [Molecules]
Notes:
Avogadro’s hypothesis was proposed by Amedeo Avogadro in 1811. It states that equal volumes of all gases, at the same temperature and pressure, contain equal numbers of molecules. Avogadro’s number is defined as 6.022×10^23 molecules per mole. This hypothesis was crucial for determining molecular weights and led to the development of the ideal gas law.
6. Which among the following is an ionic solid?
[A] Diamond
[B] Dry ice
[C] Table salt
[D] All are ionic solids
Show Answer
Correct Answer: C [Table salt]
Notes:
One important character of Ionic solids is that they readily get dissolved in water
7. Which among the following allotropes of Oxygen is found in 6 phases under various pressures and temperatures?
[A] Ozone
[B] Tetra oxygen
[C] Octaoxygen
[D] None of them
Show Answer
Correct Answer: C [Octaoxygen]
Notes:
The correct answer is Octaoxygen. Octaoxygen (O8) is an allotrope of oxygen that can exist in multiple phases under varying pressures and temperatures. It was first synthesized in 2001 and is notable for its unique molecular structure, which consists of eight oxygen atoms. Ozone (O3) is well-known but does not exhibit multiple phases like octaoxygen. Tetraoxygen (O4) is less stable and not commonly referenced in the same context.
8. Carbon monoxide poisoning is the most common type of fatal air poisoning in many parts of the world. What makes it such a fatal gas?
[A] CO dissolves in cytoplasm and functions as an inhibitor of the crucial enzymes for metabolism
[B] CO competes with Haemoglobin for Oxygen intake
[C] CO dissolves in blood Plasma and spreads toxicity
[D] CO converts into Carbon Dioxide in presence of water in Blood
Show Answer
Correct Answer: B [ CO competes with Haemoglobin for Oxygen intake]
Notes:
Carbon monoxide is colourless, odourless, and tasteless, but highly toxic because it combines with haemoglobin to produce carboxyhemoglobin, which usurps the space in haemoglobin that normally carries oxygen, but is ineffective for delivering oxygen to bodily tissues. Concentrations as low as 667 ppm may cause up to 50% of the body’s hemoglobin to convert to carboxyhemoglobin. The impact is irreversible and that is why that even after available of oxygen, the carboxyhemoglobin does not allow the Oxygen to be taken up.
9. Why most of the aromatic hydrocarbons burn with a sooty flame?
[A] Because the carbon-hydrogen ratio in aromatic compounds is high
[B] Because of the presence of the strong carbon-carbon bonds
[C] Because, hydrocarbons are unsaturated
[D] Because the carbon-hydrogen ratio in aromatic compounds is low
Show Answer
Correct Answer: A [ Because the carbon-hydrogen ratio in aromatic compounds is high]
Notes:
Because the carbon-hydrogen ratio in aromatic compounds is high.
10. What is the atomic number of Barium?
[A] 54
[B] 56
[C] 58
[D] 60
Show Answer
Correct Answer: B [56]
Notes:
The atomic number of barium is 56.
