Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. What are Sodium Alkyl Sulphate and Benzene Sulphate examples of?
[A] Explosives
[B] Insecticides
[C] Fungicides
[D] Synthetic Detergents
Show Answer
Correct Answer: D [Synthetic Detergents]
Notes:
Sodium Alkyl Sulphate and Benzene Sulphate are typical examples of Synthetic Detergents. Synthetic detergents are man-made cleansing agents that function similarly to soap. These compounds were developed during World War II when a shortage of natural oils led to a search of alternative substances. The advanced features of synthetic detergents include improved cleansing efficacy, resistance to water hardness, and the ability to function in acidic conditions.
2. Which of the following statements about the chemical nature of Diamond and Graphite is incorrect?
[A] The density of Diamond is greater than that of Graphite
[B] Diamond is chemically unreactive whereas Graphite mildly reacts with certain elements
[C] Both Diamond and Graphite are excellent conductors of electricity
[D] None of the above statements is incorrect
Show Answer
Correct Answer: C [Both Diamond and Graphite are excellent conductors of electricity]
Notes:
Diamond and graphite are both forms of carbon but they exhibit different properties due to variations in their bonding arrangements. Diamond does not conduct electricity as each carbon atom in diamond is covalently bonded to four other carbon atoms, leaving no free electrons to conduct electricity. On the other hand, graphite is a good conductor of electricity due to its layered structure which leaves free electrons between the layers.
3. Which among the following basic atoms are must in an Alkaloid?
[A] Sodium
[B] Nitrogen
[C] Magnesium
[D] Potassium
Show Answer
Correct Answer: B [Nitrogen]
Notes:
Alkaloids are a class of naturally occurring organic compounds that mostly contain basic nitrogen atoms. Nitrogen is essential in their structure, contributing to their pharmacological properties. Common examples of alkaloids include morphine, caffeine, and nicotine, all of which contain nitrogen. Sodium, magnesium, and potassium are not fundamental components of alkaloids.
4. Which of the following elements is not a member of the Carbon Group in the periodic table?
[A] Silicon
[B] Germanium
[C] Tin
[D] Selenium
Show Answer
Correct Answer: D [Selenium]
Notes:
The Carbon Group of the periodic table includes the elements carbon, silicon, germanium, tin, lead, and flerovium. These elements have four electrons in the outermost shell. Selenium, however, is not a part of this group. It is a member of the Chalcogens and sits beneath Oxygen in the periodic table. The element number for Selenium is 34. It is known for its photovoltaic and photocatalytic properties.
5. Ekaboron was an element predicted by Mendeleev and he leaved a space for it in his Periodic Table. Later Ekaboron was identified with _____?
[A] Gallium
[B] Scandium
[C] Technitium
[D] Germanium
Show Answer
Correct Answer: B [Scandium]
Notes:
Ekaboron was predicted by Dmitri Mendeleev in 1871, who left a space in his Periodic Table for it. It was later identified as Scandium (element 21) in 1879 by Lars Fredrik Nilson. Scandium shares similar properties with Ekaboron, aligning with Mendeleev’s predictions.
6. Which among the following makes Chile saltpetre different from saltpetre?
[A] Nitrate
[B] Sodium
[C] Magnesium
[D] Calcium
Show Answer
Correct Answer: B [Sodium]
Notes:
Chile saltpetre, or sodium nitrate (NaNO3), differs from regular saltpetre, which typically refers to potassium nitrate (KNO3). Chile saltpetre is primarily composed of sodium, while traditional saltpetre contains potassium. Historically, Chile saltpetre was extensively mined in the Atacama Desert and was crucial for fertilizer and explosives in the 19th century.
7. 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.
8. Why most of the aromatic hydrocarbons burn with a sooty flame?
[A] Because the carbon-hydrogen ratio in aromatic compounds is high
[B] Because of the presence of the strong carbon-carbon bonds
[C] Because, hydrocarbons are unsaturated
[D] Because the carbon-hydrogen ratio in aromatic compounds is low
Show Answer
Correct Answer: A [ Because the carbon-hydrogen ratio in aromatic compounds is high]
Notes:
Because the carbon-hydrogen ratio in aromatic compounds is high.
9. The largest component of Coal gas is__?
[A] Methane
[B] Hydrogen
[C] Carbon Dioxide
[D] Carbon Monoxide
Show Answer
Correct Answer: B [ Hydrogen]
Notes:
Typical composition of the Coal gas is as follows: •Hydrogen 50% •Methane 35% •Carbon monoxide 10% •Ethylene 5%
10. What is Tyndall effect?
[A] scattering of a beam of light by the particles of a suspension
[B] refraction of a beam of light by the particles of a solution
[C] scattering of a beam of light by the particles of a colloid
[D] reflection of a beam of light by the particles of a suspension
Show Answer
Correct Answer: C [scattering of a beam of light by the particles of a colloid]
Notes:
The scattering of a beam of light by the particles of a colloid is called the Tyndall effect.