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 iron ore contains the highest percentage of iron content?
[A] Hematite
[B] Siderite
[C] Magnetite
[D] Limonite
Show Answer
Correct Answer: C [Magnetite]
Notes:
Magnetite (Fe3O4) typically contains about 70% iron by weight. It is black in color and strongly magnetic. Hematite (Fe2O3) contains about 60–70% iron. Limonite contains 35–50% iron. Siderite (FeCO3) contains about 48% iron. Magnetite is widely mined due to its high iron concentration compared to other ores.
2. 2,4-D, which is sold as a weed killer of the broad-leaved weeds is a synthetic version of __:
[A] Auxin Hormone
[B] Cytokinin Hormone
[C] Xylitol
[D] None of them
Show Answer
Correct Answer: A [Auxin Hormone ]
Notes:
2,4-dichlorophenoxyacetic acid (2,4-dichlorophenoxyethanoic acid) is a synthetic auxin frequently used as a weed killer of broad-leaved weeds. When two herbicides 2,4,5-T and 2,4-D and mixed in equal parts, it is called Agent Orange, which was used by US in Vietnam war.
3. Which of the following processes commonly use the method of adsorption?
[A] Scrubbers manufacturing
[B] Purification of solid substances
[C] Chromatography
[D] Purification of liquid substances
Show Answer
Correct Answer: C [Chromatography]
Notes:
Adsorption, the binding of gas or liquid particles to a solid surface, is often used in chromatography – a laboratory technique for the separation of a mixture. This process is critical as it allows the separation of the compounds in the mixture, thereby enabling further analysis or purification. Apart from chromatography, adsorption is also used in scrubbers and purification of solids and liquids.
4. Which among the following gas is used in Balloons?
[A] Hydrogen
[B] Helium
[C] Nitrogen
[D] Oxygen
Show Answer
Correct Answer: B [Helium]
Notes:
The correct answer is Helium. Helium is a non-flammable, lighter-than-air gas, making it safe for use in balloons. Unlike hydrogen, which is highly flammable and poses explosion risks, helium is inert and does not react with other substances. Helium is the second most abundant element in the universe, primarily produced through nuclear fusion in stars. It was first discovered in the sun before being found on Earth.
5. The chemical oxygen demand COD test is commonly used to measure which of the following?
[A] amount of organic compounds in water
[B] amount of oxygen in water
[C] amount of oxygen in a chemical
[D] amount of oxygen used in a oxygenation process
Show Answer
Correct Answer: A [amount of organic compounds in water]
Notes:
chemical oxygen demand is a measure of water quality and is amount of organic pollutants found in surface water. Potassium permanganate has been used for many years to measure COD
6. What term refers to the minimum temperature at which a combustible substance begins to ignite?
[A] Fireless Temperature
[B] Ignition Temperature
[C] Static Temperature
[D] Optimum Temperature
Show Answer
Correct Answer: B [Ignition Temperature]
Notes:
The term for the minimum temperature necessary to ignite a combustible substance is “Ignition Temperature”. It plays a critical role in fire safety and in the field of thermodynamics. Incorrect handling of substances with low ignition temperatures can lead to hazardous situations like unexpected fires or explosions. Additionally, understanding a material’s ignition temperature helps in proper storage and safe handling to prevent unwanted accidents.
7. Which of the following is the most common naturally occurring form in which silicon is found?
[A] Oxide
[B] Fluoride
[C] Nitride
[D] Sulphide
Show Answer
Correct Answer: A [ Oxide ]
Notes:
Silica is also known as Silicon dioxide, is the most prevalent form of naturally occurring silicon.
8. Which of the following is not a form of brass?
[A] Dutch metal
[B] Prince’s metal
[C] Field’s metal
[D] Muntz metal
Show Answer
Correct Answer: C [Field’s metal]
Notes:
Field’s metal is an alloy of bismuth, indium, and tin, with the following percentages by weight: 32.5% Bi, 51% In, 16.5% Sn. Dutch metal, Prince’s metal and Muntz metal are a form of brass.
9. What do we call the process of converting an ore into its oxide by heating it in a limited supply of air below its melting point?
[A] Roasting
[B] Calcination
[C] Leaching
[D] Liquation
Show Answer
Correct Answer: B [Calcination]
Notes:
Calcination is the process of converting an ore into its oxide by heating it in a limited supply of air or in absence of air, below its melting point. It is used to convert the concentrated ore to its oxide.
10. What is the bond formed due to the electrostatic attraction known as?
[A] Covalent bond
[B] Electrovalent bond
[C] Electromagnetic bond
[D] Polar bond
Show Answer
Correct Answer: B [Electrovalent bond]
Notes:
The bond formed, as a result of the electrostatic attraction between the positive and negative ions is termed as Electrovalent bond. It is also known as Ionic bond.