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. Which among the following is an example of a Chemical Change?
[A] Rusting of iron
[B] Magnetisation of iron
[C] Melting of iron
[D] Heating of iron
Show Answer
Correct Answer: A [Rusting of iron ]
Notes:
Rust is an iron oxide, a usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture. Rusting of Iron is a chemical change.
3. Which among the following is known as Quick Lime?
[A] CaO
[B] CaCO2
[C] Ca(OH)2
[D] CaCl2
Show Answer
Correct Answer: A [CaO]
Notes:
Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature.
4. Which acid is described as HOOCCOOH?
[A] Oxalic Acid
[B] Acetic Acid
[C] Carbonic Acid
[D] Citric Acid
Show Answer
Correct Answer: A [Oxalic Acid]
Notes:
Oxalic acid is an organic compound with the formula C₂H₂O₄. Some call it “crab acid” due to its appearance. Its condensed formula is HOOCCOOH, reflecting its classification as the simplest dicarboxylic acid.
5. What are the essential components used in the production of Nitrolim, a fertilizer extensively used in the past?
[A] Nitrogen & Limestone
[B] Calcium Carbide and Nitrogen
[C] Calcium Carbide & Carbon
[D] Calcium Carbide and Limestone
Show Answer
Correct Answer: B [Calcium Carbide and Nitrogen]
Notes:
Nitrolim is a type of fertilizer that was widely used in the past. The main components of Nitrolim are calcium carbide and nitrogen. Calcium carbide reacts with nitrogen to form calcium cyanamide, which is an active ingredient in Nitrolim. This fertilizer is significant as it helps in fixing nitrogen in the soil thereby promoting plant growth.
6. Which of the following is the correct term used to describe Graphite, Carbon and Diamonds?
[A] Isotopes
[B] Isomers
[C] Isotones
[D] Allotropes
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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.
7. Which of the following is not a common use of Graphite?
[A] Manufacturing of electrodes
[B] As a lubricant
[C] Manufacturing of crucibles
[D] In glass cutting
Show Answer
Correct Answer: D [In glass cutting]
Notes:
Graphite is renowned for its conspicuous uses owing to its unique properties like its ability to conduct electricity, which makes it ideal for electrode manufacturing. It’s also used as a lubricant and in the production of crucibles, thanks to its high melting point. However, it isn’t used in glass cutting.
8. Which among the following is Quick Silver?
[A] Aluminium
[B] Mercury
[C] Lead
[D] Zinc
Show Answer
Correct Answer: B [Mercury]
Notes:
Mercury is a chemical element with the symbol Hg and atomic number 80. The element is also known as quicksilver for its mobility. Mercury is one of the oldest and deadliest poisons, a highly toxic metal mined from a brilliant red ore.
9. 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.
10. Which among the following will undergo a chemical reaction depending on the pH of the solution?
[A] Calcium Oxide
[B] Zinc Oxide
[C] Ferric Oxide
[D] Ferrous Oxide
Show Answer
Correct Answer: B [Zinc Oxide]
Notes:
Zinc oxide (ZnO) can undergo a chemical reaction depending on the pH of the solution. In acidic conditions, it can react to form zinc ions (Zn²⁺), while in alkaline conditions, it can form zincates. This behavior is due to its amphoteric nature, which allows it to react with both acids and bases. In contrast, calcium oxide (CaO) is basic, ferric oxide (Fe₂O₃) is generally inert in neutral pH, and ferrous oxide (FeO) is less reactive in varying pH levels.