Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. 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.
2. Who among the following had given the Atomic Theory?
[A] Benzamin Franklin
[B] Madam curie
[C] Albert Einstien
[D] John Dalton
Show Answer
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.
3. How many parts are of other metals in a 17 carat Gold?
[A] 3
[B] 5
[C] 7
[D] 9
Show Answer
Correct Answer: C [7]
Notes:
In 17 carat gold, the composition is 17 parts gold and 7 parts other metals, making it 70.6% gold. The term “carat” refers to the purity of gold, with 24 carats being pure gold. Thus, 17 carat gold contains 7 parts of other metals, which can include copper, silver, or palladium, used to enhance durability and alter color.
4. Sodium bicarbonate decomposes above 70 °C, making it usable in bakery products. What end product of this thermal decomposition process contributes to its use in baking?
[A] Hydrogen
[B] Carbon Dioxide
[C] Water Vapor
[D] Sodium Carbonate
Show Answer
Correct Answer: B [Carbon Dioxide]
Notes:
Sodium bicarbonate, commonly known as baking soda, is used in baking due to its ability to decompose above 70 degrees Celsius and release carbon dioxide. This chemical reaction is given by the equation 2 NaHCO3 – Na2CO3 + H2O + CO2. In baking, it reacts with other ingredients or decomposes at high temperatures to produce carbon dioxide, which causes the dough to rise, creating the fluffy texture in baked goods.
5. 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.
6. What do we call the energy required to remove loosely bound electron from an atom?
[A] Excitation energy
[B] Atom energy
[C] Ionization energy
[D] Shell energy
Show Answer
Correct Answer: C [Ionization energy]
Notes:
Ionization energy is the quantity of energy required to remove loosely bound electron from an atom.
7. Choose the incorrect pair?
[A] Washing soda – Sodium Carbonate
[B] Caustic soda – Sodium Hydrogencarbonate
[C] Acetic acid – Ethanoic acid
[D] Bleaching powder – Calcium oxide
Show Answer
Correct Answer: D [Bleaching powder – Calcium oxide]
Notes:
Sodium carbonate is commonly known as Washing soda. Sodium Hydrogencarbonate is commonly known as Caustic soda. Ethanoic acid is commonly known as Acetic acid. calcium oxychloride is commonly known Bleaching powder.
8. Which of the following Metal-Ore pairs is not correct?
[A] Iron – Magnetite
[B] Aluminium – Bauxite
[C] Gold – Calaverite
[D] Calcium – Carnalite
Show Answer
Correct Answer: D [Calcium – Carnalite]
Notes:
Carnalite is an ore of Potassium. It’s a hydrated potassium magnesium chloride. The chemical formula of Carnalite is KCl. MgCl2 . 6H2O.
9. What do we call the region of space around the nucleus where the probability of finding an electron is maximum?
[A] Shell
[B] sub-shell
[C] Orbital
[D] electron cloud
Show Answer
Correct Answer: C [Orbital]
Notes:
The region of space around the nucleus where the probability of finding an electron is maximum is called an orbital. The electron cloud is a visual model that represents all the orbitals in an atom
10. Which of the following statements is correct about Beta-decay?
[A] In β+decay, Mass number increases by 2
[B] In β−decay, Mass number decreases by 2
[C] In β−decay, the atomic number increases by 1
[D] None of the above
Show Answer
Correct Answer: C [In β−decay, the atomic number increases by 1]
Notes:
In both β− and β+ decay, the mass number A remains unchanged. In β− decay, the atomic number of the nucleus goes up by 1, while in β+ decay, the atomic number goes down by 1.
