Chemistry MCQ Quiz - Objective Question with Answer for Chemistry - Download Free PDF

CONCEPT:

Dimerization of Nitrogen Oxides

• Some nitrogen oxides can undergo dimerization under specific conditions to form stable dimers.
• Dimerization usually occurs when the monomer has an unpaired electron or is a free radical. This allows the molecules to pair up and stabilize by forming a covalent bond or through other interactions.

EXPLANATION:

• NO₂ (Nitrogen dioxide): This molecule has an unpaired electron, making it a free radical. As a result, it can dimerize to form N₂O₄ (dinitrogen tetroxide) under suitable conditions, such as low temperatures.

Therefore, the nitrogen oxide that may dimerize is NO₂.

Reaction for dimerization of NO₂:

2NO₂ → N₂O₄

The correct answer is Vitamin C.

Concept:

• Vitamins are organic substances that we need in sufficient quantities to maintain good health.
• Our body, however, cannot synthesize them. Therefore, we need to consume natural sources such as fruits and vegetables.
• Vitamins are divided into two groups– water-soluble vitamins (Vitamins of B group and Vitamin C) and fat-soluble vitamins (Vitamins A, D, E, and K).

Explanation:

• Vitamin C is the vitamin that is destroyed by heat during cooking.
• When we boil something that contains vitamin C, it reduces its content more than any other method of cooking.
• Broccoli, spinach, and lettuce, for example, lose up to or more than 50% of their vitamin C when they are cooked.
• Water-soluble vitamins are also temperature-sensitive vitamins.
• When the temperature drops below 86°F, vitamin C begins to denature.
• Vitamin C is primarily found in oranges, strawberries, tomatoes, broccoli, and green peppers, among other fruits and vegetables.
• When vitamin C is exposed to air, it is easily destroyed, which is what happens when food is overheated.
• When fat-soluble vitamins are heated or exposed to air, they are not destroyed.

The correct answer is E.

Key Points

• Vitamin E is tocopherol.
• Vitamin E represents a group of compounds that contain both tocopherol and tocotrienol.
  • It is good for the immune system and it fights toxins.
  • It is a fat-soluble vitamin.
  • It is a very powerful antioxidant.
  • Weak muscles and fertility problems are signs of deficiency of vitamin E.
  • Its deficiency also causes hair damage and skin problems.

Important Points

CONCEPT:

Terminal Oxygen Atoms in Chemical Compounds

• Terminal Oxygen Atoms: These are oxygen atoms that are at the end of a bond or functional group, typically attached to a central atom (like chromium in this case) and are not involved in further bonding.
• Chemical Reactions: The reactions provided involve chromium compounds, where the terminal oxygen atoms come from the formation of the dichromate ion (Cr₂O₇²⁻) in the final compound.

EXPLANATION:

Therefore, the correct answer is: The number of terminal "O" present in compound C is 6.

CONCEPT:

Determining the Percentage of Carbon in an Organic Compound

%C = (mass of C in the compound / mass of the compound) × 100

• When an organic compound undergoes combustion, it reacts with oxygen to form CO₂ and H₂O. From the masses of CO₂ and H₂O produced, the percentage of carbon and hydrogen in the compound can be calculated.
• The mass of carbon in CO₂ is calculated by finding the moles of CO₂ produced, then multiplying by the molar mass of carbon (12 g/mol).
• The percentage of carbon in the compound is then calculated using the formula:

EXPLANATION:

• Given:
  • Mass of organic compound = 0.5 g
  • Mass of CO₂ produced = 1.46 g
  • Mass of H₂O produced = 0.9 g
• To calculate the mass of carbon in the compound:
  • Moles of CO₂ = mass of CO₂ / molar mass of CO₂
  • Molar mass of CO₂ = 12 (for C) + 32 (for O) = 44 g/mol
  • Moles of CO₂ = 1.46 g / 44 g/mol = 0.03318 mol
  • Since each mole of CO₂ contains 1 mole of carbon, the moles of carbon in the compound are also 0.03318 mol.
  • Mass of carbon = moles of carbon × molar mass of carbon = 0.03318 mol × 12 g/mol = 0.3982 g
• Now, calculate the percentage of carbon in the compound:

  %C = (0.3982 g / 0.5 g) × 100 = 79.64%

Therefore, the percentage of carbon in the compound is: 80% (rounded to the nearest integer).

The correct answer is Antipyretic.

• Antipyretic is a drug that reduces fever.
  • Antipyretics cause the hypothalamus to override a prostaglandin-induced increase in temperature.
  • The body then works to lower the temperature, which results in a reduction in fever. 

Additional Information

• Barbiturates are a type of central nervous system (CNS) depressant used to treat insomnia, seizures, and headaches​.
• Antiseptic slows or stops the growth of micro-organisms on external surfaces of the body and helps to prevent infections.
• Antibiotics include a range of powerful drugs that kill bacteria or slow their growth. 
  • They treat bacterial infections. 

The correct answer is Na2CO3.

Key Points

• The sodium compound is used for softening hard water. Washing soda or sodium carbonate is used for removing the permanent hardness of the water.
• Washing soda has a chemical formula Na₂CO₃.10H2O.
• It binds calcium and magnesium molecules in water.
• Water can be softened by adding sodium carbonate (washing soda) or bypassing the water through an ion-exchange column.
• For large-scale municipal operations, a process known as the lime-soda process is used to remove Ca²⁺ and Mg²⁺ from the water supply.
•  

Additional Information

The correct answer is E.

Key Points

• Vitamin E is tocopherol.
• Vitamin E represents a group of compounds that contain both tocopherol and tocotrienol.
  • It is good for the immune system and it fights toxins.
  • It is a fat-soluble vitamin.
  • It is a very powerful antioxidant.
  • Weak muscles and fertility problems are signs of deficiency of vitamin E.
  • Its deficiency also causes hair damage and skin problems.

Important Points

Bleaching powder by its nature is an Oxidising agent.

• Stable bleaching powder is widely used as a disinfectant in water purification, as well as in the textile and pulp and paper industries.
• "Bleaching powder" is made by the action of chloride gas on calcium hydroxide.
• The reaction being essentially:
• 2Ca (OH)₂ + 2Cl₂ → Ca(OCl)₂ + CaCl₂ + 2H₂O.
• In the production of bleaching powder, slaked lime spread on the floors of large rectangular chambers of lead or concrete is exposed to chlorine gas.
• Bleaching powder, a solid combination of chlorine and slaked lime, was introduced in 1799 by Scottish chemist Charles Tennant.

The correct answer is Sugar in water.

Key Points

• The physical properties help in separating the homogenous mixtures.
• Those mixtures in which the substances are completely mixed together and are indistinguishable from one another are called homogeneous mixtures.
• A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture.
• Many homogeneous mixtures are commonly referred to as solutions.
• Some of the examples of homogeneous mixtures (or solutions) are Sugar solution, Salt solution, Copper sulphate solution, Seawater, Alcohol and water mixture, Petrol and oil mixture, Soda water etc.

• Heterogeneous mixture:
  • A heterogeneous mixture is a mixture with a non-uniform composition that contains components in different phases.
  • The composition varies from one region to another with at least two phases that remain separate from each other, with clearly identifiable properties.
  • Heterogeneous mixtures contain particles that retain their chemical properties when they are mixed and can be distinguished after they are mixed.
  • The components of heterogeneous mixtures can be separated by the filtration of chemical procedures.
  • The two types of heterogeneous mixtures are suspensions and colloids.
  • Sugar and sand form a heterogeneous mixture. If you look closely, you can identify tiny sugar crystals and particles of sand.
  • Ice cubes in cola form a heterogeneous mixture.

The correct answer is A reducing agent.

Key Points

• Hydrogen peroxide H₂O₂ is acting as a reducing agent here.
• A reducing agent is a compound that oxidises itself and reduces the other compound in a chemical reaction.
• A reducing agent will lose electrons in a chemical reaction, and thus get oxidized.
• Here, the charge on Chlorine (Cl) is earlier 0, but after reaction, the charge on each Cl atom is -1, this shows that it has been reduced. Thus, Hydrogen peroxide has worked as a reducing agent.
• Also, in terms of hydrogen, adding hydrogen is termed as reduction, whereas removing it is termed as oxidation. Since hydrogen is added to chlorine, chlorine is reducing, and hence we can say that Hydrogen peroxide has worked as a reducing agent.

The correct answer is Increase.

Concept:

• Molarity:
  • It is defined as the moles of a solute per litres of a solution.
  • It is also known as the molar concentration of a solution.
• Molality:
  • It is defined as the number of moles of solute per kilogram of solvent.
• Mole fraction:
  • It is the ratio of moles of a component with the total moles of solute and solvent.
• Mass%:
  • It is the percentage of the mass of solute or solvent w.r.t total mass of solution.
• Formulas:

Explanation:

• Molarity depends on the volume of the solution.
• And volume is directly proportional to temperature.
• And when we increase the temperature the volume will increase.
• So the increase in volume leads to a decrease in Molarity as Molarity is inversely proportional to the volume of solution.

​Additional Information

Notes:

• Normality:
  • It is defined as the number of gram equivalent per litre of solution.
  • Also known as equivalent concentration.
  • Normality = Number of gram equivalents / [volume of solution in litres]
• Normality is inversely proportional to temperature.
• ​Volume is directly proportional to temperature.
• Molarity is inversely proportional to volume.
• Molarity is inversely proportional to temperature.
• Molality is not dependent on temperature.

The correct answer is Bauxite.Key Points

• Bauxite is an aluminium-rich sedimentary rock formed from laterite soil.
• It is found in tropical or subtropical regions.
• Bauxite is used for the production of Aluminium.
• Bauxite is a non-ferrous metallic mineral that is used in the manufacturing of aluminium.
• Bauxite is found mainly in tertiary deposits and is associated with laterite rocks.

 Important Points

• Odisha is the largest bauxite-producing state in India.
• More than half of India's bauxite deposits are found in Odisha.
• Bauxite is an important mineral used in the production of aluminium.

 Additional Information

Important ores:

The correct answer is Nitric acid.

• Nitric acid is used in the purification of gold and silver.

Key Points

• Nitric acid is used in the purification of gold. The acid mixture aqua regia, or royal water, dissolves gold and is used to purify scrap alloy containing gold.
  • Aqua regia is a mixture of hydrochloric acid and nitric acid in a 3:1 ratio.
  • Nitric acid is a nitrogen oxoacid of formula HNO3 in which the nitrogen atom is bonded to a hydroxy group and by equivalent bonds to the remaining two oxygen atoms.

Important Points

The correct answer is Uracil.

Key Points

• In DNA, Adenine, Guanine, Thymine, and Cytosine are present.
• In RNA Adenine, Guanine, Cytosine, and Uracil are present.
• Uracil
  • It is one of the four nucleobases in nucleic acid RNA.
  • In DNA, Uracil nucleobases are replaced by thymine.
  • Its formula is C₄H₄N₂O_2.

_{Additional Information}

•  Guanine
  • It is one of the four main nucleobases found in the nucleic acids DNA and RNA.
  • It is used to make one of the building blocks of DNA and RNA.
• Adenine
  • It is also one of the four main nucleobases found in the nucleic acids DNA and RNA.
  • It is part of many substances in the body that give energy to cells.
• Cytosine
  • It is pyrimidine and one of the nitrogenous bases found in RNA and DNA acid for making genetic code.
  • It Plays an essential role in forming base pairs by bonding with guanine.