Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. What is commonly referred to as “Laughing Gas”?
[A] Nitric oxide
[B] Nitrous oxide
[C] Nitrogen penta oxide
[D] Nitrogen
Show Answer
Correct Answer: B [Nitrous oxide]
Notes:
Nitrous oxide is often referred to as “Laughing Gas” due to the euphoric effect it produces when inhaled. Its chemical formula is N2O and it is an oxide of nitrogen. At room temperature, it is a colorless, non-flammable gas with a relatively sweet odor and taste. It is primarily used in dentistry and surgery for its analgesic and anesthetic properties. It is also noted for its role as a major greenhouse gas and air pollutant, as well as a natural regulator of stratospheric ozone.
2. 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
3. Which among the following basic atoms are must in an Alkaloid?
[A] Sodium
[B] Nitrogen
[C] Magnesium
[D] Potassium
Show Answer
Correct Answer: B [Nitrogen]
Notes:
Alkaloids are a class of naturally occurring organic compounds that mostly contain basic nitrogen atoms. Nitrogen is essential in their structure, contributing to their pharmacological properties. Common examples of alkaloids include morphine, caffeine, and nicotine, all of which contain nitrogen. Sodium, magnesium, and potassium are not fundamental components of alkaloids.
4. Normal” rainfall is slightly acidic (and a pH of 5.6 has been assigned which might be somewhere near 5 ) because of the presence of _______?
[A] Nitric Oxide
[B] Sulphuric Acid
[C] Nitric Acid
[D] Carbonic Acid
Show Answer
Correct Answer: D [Carbonic Acid]
Notes:
Normal rainfall is slightly acidic due to the presence of carbonic acid, which forms when carbon dioxide (CO2) dissolves in water. The pH of normal rainwater is typically around 5.6, making it mildly acidic. This natural acidity is a result of the CO2 in the atmosphere, which is produced by respiration, combustion, and other natural processes.
5. What is the nature of an aqueous solution of Sodium Acetate?
[A] Acidic
[B] Basic
[C] Neutral
[D] Either acidic or basic, depending on the temperature of the solution
Show Answer
Correct Answer: B [Basic]
Notes:
An aqueous solution of sodium acetate is basic in nature. This is because sodium acetate is a salt derived from a strong base (sodium hydroxide) and a weak acid (acetic acid). When dissolved in water, it undergoes hydrolysis to form sodium ions and acetate ions. The acetate ions react with water to form acetic acid and hydroxide ions, thus creating a basic solution.
6. Which among the following is the correct impact of the London Forces in the Cycloalkanes?
[A] The melting and boiling points get increased
[B] The Melting and boiling points get decreased
[C] There is not impact on the melting and boiling points
[D] The melting point increases but boiling point decreases
Show Answer
Correct Answer: A [The melting and boiling points get increased]
Notes:
Please note that the Cycloalkanes with more than 20 carbon atoms are called Cycloparaffins. The cycloalkanes have the same properties as the alkanes but they have `Higher Boiling & Melting points`. This is because of the stronger dispersion forces between the atoms known as London Forces.
7. Consider the following substances:
- Iodine
- Naphthalene
- Camphor
Which of the above substances undergo ‘sublimation’ on heating?
[A] Only 1 and 2
[B] All of them
[C] Only 2 and 3
[D] Only 1 and 3
Show Answer
Correct Answer: B [All of them]
Notes:
Sublimation is a transition from solid to gas, bypassing the liquid phase. Iodine sublimes, producing violet vapors; naphthalene sublimes, hence its use in mothballs; and camphor also sublimes, used in medicinal and aromatic applications. Thus, all three substances exhibit sublimation upon heating, making ‘All of them’ the correct answer.
8. 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.
9. Which of the following is NOT correct about Group 14 elements?
[A] All of them are solids
[B] Melting points are much higher than those of corresponding elements of group 13
[C] Carbon is a non-metal
[D] Germanium is a metal
Show Answer
Correct Answer: D [Germanium is a metal]
Notes:
All members of group 14 are solids. Carbon and silicon are non-metals, germanium is a metalloid, whereas tin and lead are soft metals. Melting points and boiling points of group 14 elements are much higher than those of corresponding elements of group 13.
10. Which of these is NOT a compound of carbon?
[A] Acetic acid
[B] Chloroform
[C] Caustic Soda
[D] Methane
Show Answer
Correct Answer: C [Caustic Soda]
Notes:
Caustic soda is a compound of sodium where as Acetic acid, Chloroform and Methane are the compounds of carbon.
