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 happens in an oxidation reaction ?
[A] Electrons are gained
[B] Electrons are lost
[C] Protons are gained
[D] Protons are lost
Show Answer
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.
2. According to Avogadro’s hypothesis, equal volumes of gases contain equal number of?
[A] Atoms
[B] Molecules
[C] Particles
[D] Electrons
Show Answer
Correct Answer: B [Molecules]
Notes:
Avogadro’s hypothesis was proposed by Amedeo Avogadro in 1811. It states that equal volumes of all gases, at the same temperature and pressure, contain equal numbers of molecules. Avogadro’s number is defined as 6.022×10^23 molecules per mole. This hypothesis was crucial for determining molecular weights and led to the development of the ideal gas law.
3. An Jewellery was left exposed to the atmosphere for some time and it becomes coated with green carbonate. The Jewellery is made up of which of the following?
[A] Copper
[B] Silver
[C] Zinc
[D] Gold
Show Answer
Correct Answer: A [Copper]
Notes:
The correct answer is Copper. When copper jewelry is exposed to air and moisture, it reacts with carbon dioxide and water, forming copper carbonate, which appears as a green patina (often called verdigris). This process is known as oxidation. Unlike copper, silver and gold do not typically form green coatings. silver may tarnish to a black color due to silver sulfide formation, while gold is highly resistant to corrosion and tarnishing.
4. Which among the following gives hissing sound when dissolved into H2O?
[A] CaCO2
[B] Ca(OH)2
[C] CaO
[D] CaCl2
Show Answer
Correct Answer: C [CaO]
Notes:
The correct answer is CaO (calcium oxide), which is also known as quicklime. When CaO is dissolved in water, it reacts exothermically to form calcium hydroxide (Ca(OH)2), producing a hissing sound due to the rapid release of heat and steam. This reaction is a classic example of a vigorous exothermic reaction in chemistry. Calcium oxide is commonly used in construction and as a drying agent.
5. Which set shows copper ores as Sulfide, Carbonate, Silicate respectively?
[A] Chalcopyrite, Azurite, Dioptase
[B] Azurite, Dioptase, Chalcopyrite
[C] Dioptase, Chalcopyrite, Azurite
[D] Dioptase, Azurite, Chalcopyrite
Show Answer
Correct Answer: A [Chalcopyrite, Azurite, Dioptase]
Notes:
Chalcopyrite is a major copper sulfide ore. Azurite is a copper carbonate mineral with formula Cu₃(CO₃)₂(OH)₂. Dioptase is a copper silicate mineral with formula CuSiO₃·H₂O. These match the deposit types in sulfide, carbonate, and silicate order respectively.
6. Which of the following elements have the lowest and highest boiling point in the Periodic table?
[A] Helium and Tungsten
[B] Hydrogen and Rhenium
[C] Helium and Rhenium
[D] Hydrogen and Tungsten
Show Answer
Correct Answer: C [ Helium and Rhenium]
Notes:
Helium has the lowest boiling point of all the elements at –452.074°F (–268.93°C) followed by hydrogen –423.16°F (–252.87°C). The highest boiling point for an element is that of Rhenium 10,104.8°F (5,596°C) followed by tungsten 10,031°F (5,555°C).
7. Consider the following:
- Hydrogen (H2)
- Carbon monoxide (CO)
- Carbon dioxide (CO2)
- Methane (CH4)
Which of the above is/are component(s) of high-quality (100% pure) Syngas?
[A] 1 Only
[B] 1 & 2 Only
[C] 1, 2 & 3 Only
[D] 1, 2, 3 & 4
Show Answer
Correct Answer: B [ 1 & 2 Only]
Notes:
The high-quality (100% Pure) Syngas has the main components of (H2 + CO)
8. Plumbism is a condition which occurs due to accumulation of:
[A] Lead in the body
[B] Sodium in the body
[C] Cadmium in the body
[D] Potassium in the body
Show Answer
Correct Answer: A [ Lead in the body]
Notes:
Plumbism is also known as lead poisoning or a condition which occurs when there is accumulation of lead in body, usually over a few months' time period and even years.
9. Which of the following chemicals is also known as “Chinese snow”?
[A] Silver iodide
[B] Potassium nitrate
[C] Ammonium chloride
[D] Sodium phosphate
Show Answer
Correct Answer: B [ Potassium nitrate]
Notes:
Potassium nitrate is one of several nitrogen-containing compounds collectively referred to as saltpetre or saltpetre. It is also known as “Chinese snow”. Major uses of potassium nitrate are in fertilizers, rocket propellants and fireworks.
10. Which of the following is correct about Potassium carbonate?
[A] Its chemical formula is K CO3
[B] It is a salt which is white in colour
[C] It is used in the production of soap
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Potassium carbonate is a salt which is white in colour. It is used in the production of soap. Its chemical formula is K2 CO3.
