All Free Biology MCQs with Answers

• A. Acid
• B. Oxidizing agent
• C. Nitrating agent
• D. Dehydrating agent
• E. Sulfonating agent

Explanation: H2SO4 is an acid, oxidizing agent, dehydrating agent, and sulfonating agent. It is not a nitrating agent. The nitrating agent is NO2.

• A. H2SO4
• B. Ammonia
• C. Methanol
• D. NaOH
• E. Formalin

Explanation: Formalin is one of the preservatives used to preserve biological specimens. Formalin is used for the preservation of biological specimens. Formalin is 30-40% of the water in Formaldehyde or methanol.

• A. Coal tar
• B. Petroleum
• C. Coal gas
• D. Coke

Explanation: Pure carbon used as a reducing agent in industries. It is also used in the manufacture of iron and steel Industry. (Reference Sindh text book). Coal tar: A good source of hundreds of organic compounds. Petroleum: It is a viscous liquid composed of components with different boiling points. It contains alkanes,alkenes, cycloalkanes, aromatic hydrocarbons. Also called crude oil. Coal gas: Main product used as fuel. It mainly consists of methane and hydrogen.

• A. 95%
• B. 90%
• C. 85%
• D. 80%

Explanation: Duralumin is an alloy made up of 90% aluminium, 4% copper, 0.51% magnesium, and less than 1% manganese.

• A. Calcium chloride
• B. Magnesium chloride
• C. Aluminium chloride
• D. Potassium chloride

Explanation: Sodium chloride melts at a very high temperature. A mixture containing(NaCl+CaCl2) is used to decrease the melting point. The main reasons for lowering the temperature are:a) Sodium is volatile at this temperature and so a part of the metal formed may vaporize.b) At this high temperature, sodium and chlorine produced corrode the vessel.Calcium chloride, CaCl2, is added to lower the melting point of the cell medium from the normal melting point of NaCl, 804oC, to around 600oC.

• A. PVA
• B. PVC
• C. Bakelite
• D. Perspex

Explanation: Perspex is a hard, brittle, and clear polymer that is mostly used in packaging materials, bowls, toys, combs, trays, disposable cutlery, etc.PVC: a type of plastic used for pipes that carry water and for many other products. ◊ PVC is anabbreviation of "polyvinyl chloride."PVA:PVA is used in many industries, such as the textile, paper industry, and food packaging industries.Bakelite: Bakelite continues to be used for wire insulation, brake pads and related automotivecomponents, and industrial electrical-related applications.

• A. Zymase
• B. Invertase
• C. Lipase
• D. Diastase

Explanation: Lipase is an enzyme that breaks down lipid molecules. Fermentation does not involve lipid substances to be broken down, hence lipase has no use in fermentation.

• A. Al2O3
• B. P2O5
• C. Dilute H2SO4
• D. H3PO4

Explanation: There is no such reaction in which P2O5 can produce alkenes from alcohol. Dehydration of alcohols can happen through Al2O3, Dil H2SO4, and H3PO4, more about these reactions:

• A. Propionic acid
• B. Stearic acid
• C. Palmitic acid
• D. Formic acid
• E. Acetic acid

Explanation: Stearic acid (IUPAC systematic name: octadecanoic acid is one of the useful types of saturated fatty acids that comes from many animal and vegetable fats and oils.

• A. Lands Berger's method
• B. Fractional crystallization
• C. Beckmann method
• D. None

Explanation: As the solution cools, the solubility of the compound (and of the soluble impurities) decreases, the solution becomes saturated with the desired compound, and the compound begins to crystallize. Removing the solution from the crystals thus removes the solvent and the soluble impurities from the desired crystals.