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 also known as wood alcohol?
[A] Methanol
[B] Ethanol
[C] Propanal
[D] Butanol
Show Answer
Correct Answer: A [Methanol]
Notes:
Methanol (CH3OH) is also known as Wood Alcohol. It’s a solvent in many chemical processes and is a component of automobile antifreeze.
2. Which among the following is popularly called Hypo?
[A] Silver Bromide
[B] Silver nitrate
[C] Sodium thiosulphate
[D] Sodium phosphate
Show Answer
Correct Answer: C [Sodium thiosulphate ]
Notes:
Sodium thiosulfate is an important inorganic salt with several medical uses. It is also called sodium hyposulfite or ‘hypo’. It is used in several pharmaceutical preparations and also has various medical properties.
3. Which of the following is the correct term used to describe Graphite, Carbon and Diamonds?
[A] Isotopes
[B] Isomers
[C] Isotones
[D] Allotropes
Show Answer
Correct Answer: D [Allotropes]
Notes:
Allotropes refer to two or more different physical forms in which an element can exist. The property is due to different ways atoms bond together. The most common instance is the element carbon, which exists in several different forms, including diamond, graphite, and fullerenes, making it an allotropic element. It’s crucial to note that allotropy applies to elements, not compounds.
4. 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.
5. Which among the following can be used as a preservative in Tomato Juice?
[A] Sodium Chloride
[B] Sodium carbonate
[C] Sodium benzoate
[D] Sodium Lauril Sulphate
Show Answer
Correct Answer: C [Sodium benzoate]
Notes:
Sodium benzoate is commonly used as a preservative in food and beverages, including tomato juice. It inhibits the growth of mold, yeast, and some bacteria, extending shelf life. It is effective in acidic environments, such as those found in tomato products, where the pH is typically below 4.6. Sodium chloride (salt) can also act as a preservative but is primarily used for flavor. Sodium carbonate and sodium lauryl sulfate are not suitable preservatives for tomato juice.
6. Which among the following is correct statement about both rusting of iron and respiration?
[A] Both are exothermic reactions
[B] Both are endothermic reactions
[C] While Rusting is endothermic, respiration is exothermic
[D] While Rusting is exothermic, respiration is endothermic
Show Answer
Correct Answer: A [Both are exothermic reactions]
Notes:
Both are oxidation-therefore exothermic processes
7. 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.
8. Which of the following is correct about the first ionization enthalpy of alkaline earth metals?
[A] It is higher than corresponding Group 1 metals
[B] It is lower than corresponding Group 1 metals
[C] No fix pattern exist
[D] None of the above
Show Answer
Correct Answer: A [It is higher than corresponding Group 1 metals]
Notes:
The first ionization enthalpy of these metals is higher than corresponding Group 1 metals due to the small size of these elements compared to the corresponding alkali metals. The second ionization enthalpy of these metals is lower than corresponding alkali metals.
9. Which of the following is correct about ozone?
[A] it is a red coloured gas
[B] it is odourless
[C] it is harmless in small concentrations
[D] All of the above
Show Answer
Correct Answer: C [it is harmless in small concentrations]
Notes:
Pure ozone is a pale blue gas, dark blue liquid and violet-black solid. Ozone has a characteristic smell and in small concentrations it is harmless. However, if the concentration rises above about 100 parts per million, breathing becomes uncomfortable resulting in headache and nausea.
10. Which of the following is correct about the properties of a solution?
[A] The particles of a solution can be seen by naked eyes
[B] The particles of a solution scatter a beam of light passing through the solution
[C] The solute particles do not settle down when left undisturbed
[D] All of the above
Show Answer
Correct Answer: C [The solute particles do not settle down when left undisturbed]
Notes:
The particles of a solution are smaller than 1 nm in diameter. So, they cannot be seen by naked eyes. Because of very small particle size, they do not scatter a beam of light passing through the solution. The solute particles do not settle down when left undisturbed, that is, a solution is stable.
