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. The Alkali metals are called good reducing agents. This implies that__:
[A] They easily capture electrons
[B] They are not stable at room temperature
[C] They easily lose electrons
[D] They don’t act with dilute acids
Show Answer
Correct Answer: C [They easily lose electrons ]
Notes:
Alkali metals have one electron in their valence shell and hence they easily lose or donate electron.
3. Which among the following element is an essential constituent of acids?
[A] Nitrogen
[B] Hydrogen
[C] Oxygen
[D] Helium
Show Answer
Correct Answer: B [Hydrogen]
Notes:
Acids are molecules that are able to donate proton or H+ thus, hydrogen is essential for acids. However, there are exception to this such as Bronsted acids. A Bronsted acid is an acid which can accept an electron pair, but does not have a proton (H+) to donate. Examples of such acids are Aluminum Chloride (AlCl3), Boron Trifuoride (BF3).
4. White Phosphorous is represented by which among the following symbols?
[A] P1
[B] P2
[C] P3
[D] P4
Show Answer
Correct Answer: D [P4]
Notes:
The most important form of elemental phosphorus from the perspective of applications and chemical literature is white phosphorus. It consists of tetrahedral P4 molecules, in which each atom is bound to the other three atoms by a single bond. This P4 tetrahedron is also present in liquid and gaseous phosphorus up to the temperature of 800 °C when it starts decomposing to P2 molecules
5. Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.1% by weight. An increasing amount of Iron will result in which of the following?
[A] Increase Hardening
[B] Decrease Hardening
[C] Increase ductility
[D] Increase melting Point
Show Answer
Correct Answer: A [Increase Hardening]
Notes:
Increasing the amount of iron in steel generally leads to increased hardening. This is due to the formation of a solid solution where carbon atoms occupy interstitial spaces in the iron lattice, enhancing strength and hardness. Steel’s carbon content is crucial. higher carbon levels (up to 2.1%) improve hardness but reduce ductility. The melting point of steel is also influenced by its composition, but the primary effect of increasing iron is hardening.
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. 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.
8. Which among the following alkane has largely replaced the ozone layer-depleting halomethanes in household refrigerators and freezers?
[A] Methane
[B] Propane
[C] Butane
[D] Ethane
Show Answer
Correct Answer: C [Butane]
Notes:
Isobutane, which is known in the industry as R600A has been used in several domestic refrigerators in recent times because it is an excellent refrigerant and non-ozone depleting substance with low global warming potential. The only drawback is that it is highly inflammable.
9. 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
10. After a nuclear disaster, the Strontium-90 becomes an health issue of great concern. What is the major concern about this particular isotope?
[A] Strontium-90 gets deposited in the Red Blood Cells and causes Blood Cancer
[B] Strontium-90 gets deposited in the Liver cells and causes Liver Cirrhosis
[C] Strontium-90 gets deposited in bones and bone marrow and causes cancer
[D] None of the above is a correct statement
Show Answer
Correct Answer: C [ Strontium-90 gets deposited in bones and bone marrow and causes cancer]
Notes:
Strontium-90 is a “bone seeker” that exhibits biochemical behaviour similar to calcium, the next lighter Group 2 element. After entering the organism, most often by ingestion with contaminated food or water, about 70–80% of the dose gets excreted. Virtually all remaining strontium-90 is deposited in bones and bone marrow, with the remaining 1% remaining in blood and soft tissues. Its presence in bones can cause bone cancer, cancer of nearby tissues, and leukaemia.
