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 among the following acids is abundant in Grapes, Bananas and Tamarind?
[A] Lactic Acid
[B] Oxalic Acid
[C] Salicylic Acid
[D] Tartaric Acid
Show Answer
Correct Answer: D [Tartaric Acid ]
Notes:
Tartaric acid occurs naturally in many fruits such as grapes, bananas, tamarinds, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally in the process of winemaking. It is commonly mixed with sodium bicarbonate and is sold as baking powder used as a leavening agent in food preparation. The acid itself is added to foods as an antioxidant E334 and to impart its distinctive sour taste.
2. Which among the following happens in an oxidation reaction ?
[A] Electrons are gained
[B] Electrons are lost
[C] Protons are gained
[D] Protons are lost
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Correct Answer: B [Electrons are lost ]
Notes:
Oxidation is the loss of electrons during a reaction by a molecule, atom or ion. When oxidation occurs, an element loses electrons and its oxidation number increases .i.e. it becomes more positive.
3. Who among the following had given the Atomic Theory?
[A] Benzamin Franklin
[B] Madam curie
[C] Albert Einstien
[D] John Dalton
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Correct Answer: D [John Dalton]
Notes:
The correct answer is John Dalton. He proposed the Atomic Theory in the early 19th century, stating that matter is composed of indivisible atoms, each with a specific weight. Dalton’s work laid the foundation for modern chemistry. Notably, he also introduced the concept of atomic weights and was the first to use symbols to represent atoms of different elements.
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. What is the primary use of Phenolphthalein in chemistry?
[A] A Solvent
[B] A Dye
[C] A Catalyst
[D] A Detergent
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Correct Answer: B [A Dye]
Notes:
Phenolphthalein is commonly employed as a pH indicator in titrations due to its distinct color change in varying pH levels. At pH 8.2, it appears colorless but turns pink as the pH increases to 10. It is not used as a solvent, catalyst or detergent. It also finds applications in forensic science for detecting latent blood stains.
6. Which among the following were not discovered by the time , Mendeleev published his periodic table?
[A] Lathanides
[B] Actinides
[C] Noble Gases
[D] Halogens
Show Answer
Correct Answer: C [Noble Gases]
Notes:
When Mendeleev published his periodic table in 1869, noble gases had not yet been discovered. The first noble gas, argon, was identified in 1894 by Lord Rayleigh and William Ramsay. In contrast, lanthanides and actinides were recognized later, but their existence was inferred from Mendeleev’s predictions. Halogens, including elements like chlorine and iodine, were known prior to Mendeleev’s work.
7. If a Hydrogen atom is removed from a hydrocarbon of Benzene group, the remaining residue is called _________?
[A] Alkyl
[B] Aryl
[C] Arene
[D] Azene
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Correct Answer: B [Aryl]
Notes:
The correct answer is Aryl. In organic chemistry, when a hydrogen atom is removed from a benzene ring (a hydrocarbon), the remaining structure is referred to as an aryl group. Aryl groups are derived from aromatic compounds, specifically those containing a benzene ring. For example, when a hydrogen is removed from toluene (methylbenzene), the resulting aryl group is called a tolyl group. Aryl groups are important in various chemical reactions and are foundational in the synthesis of many organic compounds.
8. In a photochemical smog, which gas causes irritation to mucous membrane and respiratory system?
[A] Nitrous oxide
[B] Sulphur dioxide
[C] Ozone
[D] Carbon monoxide
Show Answer
Correct Answer: C [ Ozone]
Notes:Ozone (O3) is the most common photochemical oxidant in photochemical smog. Inhaling ozone can cause irritation to the mucous membrane and respiratory system. Ozone can also cause chest constriction and damage to vegetation.
Other components of photochemical smog include:
- Nitrogen dioxide (NO2)
- Peroxyacetylnitrate (PAN)
- Aldehydes
Other air pollutants that can be harmful to humans include:
- Sulfur dioxide
- Volatile organic compounds (VOCs)
- Dioxins
- Polycyclic aromatic hydrocarbons (PAHs)
Carbon monoxide can cause hyperventilation, respiratory distress, and stillbirths. At high levels, carbon monoxide can even cause direct poisoning.
9. Which of the following is the most common naturally occurring form in which silicon is found?
[A] Oxide
[B] Fluoride
[C] Nitride
[D] Sulphide
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Correct Answer: A [ Oxide ]
Notes:
Silica is also known as Silicon dioxide, is the most prevalent form of naturally occurring silicon.
10. The adsorption of hydrogen by palladium is termed as:
[A] Physisorption
[B] Chemisorptions
[C] Physical adsorption
[D] Occlusion
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Correct Answer: D [ Occlusion]
Notes:
The adsorption of hydrogen by palladium is called occlusion. Occlusion is a type of adsorption where gases are adsorbed onto metals. The hydrogen adsorbed onto palladium is called occluded hydrogen.
Palladium can absorb about 900 times its own volume of hydrogen. The hydrogen that is adsorbed is more active than normal hydrogen.
The adsorption of hydrogen on palladium occurs through a hydride formation. The chemical bonds that are formed cannot be broken easily to release the hydrogen gas from the surface of the metal.
The process of occlusion is used to purify hydrogen.