All Free Biology MCQs with Answers
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19844 questions · page 497 of 1985
4961. In the NaCl crystal, chloride ions present at the face center are distributed in:
- A. One Unit Cell
- B. 8 Unit Cells
- C. 4 Unit Cells
- D. 2 Unit Cells
Explanation: In the z=0 configuration below, the center chloride ion actually belongs to two unit cells in the overall crystal.
Correct answer: 2 Unit Cells4962. Graphite has a structural similarity with:
- A. B2H6
- B. B4C
- C. B
- D. BN
Explanation: H−BN or BN structure consists of an alternate arrangement of Boron and Nitrogen atoms in a 2-dimensional plane and turn, forms a hexagonal ring structure. The N and B atoms are combined by an sp2 orbital forming a strong sigma bond. Due to the formation of hexagonal rings, they share a common structure but with different atoms.
Correct answer: BN4963. A polymer called Bakelite is formed by the reaction of phenol with:
- A. Hydrogen
- B. Ethers
- C. Carboxylic acid
- D. Formaldehyde
Explanation: Option A: Hydrogen is not involved in the synthesis of Bakelite, so this answer is incorrect. Option B: Ethers are not reactive enough to react with phenol to form Bakelite, so this answer is incorrect. Option C: Carboxylic acid is not involved in the synthesis of Bakelite, so this answer is incorrect. Option D: Bakelite is formed from the reaction of phenol and formaldehyde. The reaction is as shown:
Correct answer: Formaldehyde4964. Which of the following elements is not usually present in all proteins?
- A. Carbon
- B. Hydrogen
- C. Nitrogen
- D. Sulphur
Explanation: Proteins are made from amino acids, and out of the 20 available amino acids, only two contain sulfur.
Correct answer: Sulphur4965. The activator of the phosphatase enzyme is _.
- A. Mn2+
- B. Mg2+
- C. Zn2+
- D. None of these options are correct
Explanation: It is a fact that phosphatase enzymes are activated by Mg+2 ions. Hence, option B is correct.
Correct answer: Mg2+4966. Polymerization of ethene produces which of the following polymers?
- A. Polyvinyl
- B. Polethyl
- C. Polyethylene
- D. Polyethoxy
Explanation: Ethene is polymerized to form polyethene, which is also called polyethylene.
Correct answer: Polyethylene4967. Enzymes speed up the reaction up to:
- A. 1020
- B. 2010
- C. 1040
- D. 1510
Explanation: A reaction might be sped up by an enzyme upto 1020 times the original rate.
Correct answer: 10204968. Which is the structure of polyvinyl chloride (polychloroethane)?
- A. -[CCl2-CCl2]-
- B. -[HCCl-CH-Cl]-
- C. [H2C=CH-Cl]
- D. -[H2C-CH-Cl]-
Explanation: Poly(vinyl chloride) (PVC) is a synthetic resin made from vinyl chloride and is a member of a large family of polymers broadly referred to as "vinyls." The chemical formula for vinyl chloride is H2C=CHCl, and the formula for PVC is (H2C-CHCl)n, where n is the degree of polymerization.
Correct answer: -[H2C-CH-Cl]-4969. Nylon-6,6 is also called:
- A. Poly styrene
- B. Polyester
- C. Polyamide
- D. Polyvinyl alcohol
Explanation: Nylon-6,6 is a synthetic polymer called a polyamide because of the characteristic monomers of amides in the backbone chainPolystyrene is a plastic. It is made up of many styrenes. Styrene is a small organic compound with the chemical formula C6H5CH=CH2.Polyester is a synthetic fabric that's usually derived from petroleum. This fabric is one of the world's most popular textiles, and it is used in thousands of different consumer and industrial applications. Chemically, polyester is a polymer primarily composed of compounds within the ester functional group.Poly is a water-soluble synthetic polymer. It has the idealized formula [CH₂CH]ₙ.
Correct answer: Polyamide4970. Which one of the following is the structure of Teflon?
- A. (-CF2-CF2-)n
- B. (-CF2-CCl2-)n
- C. (-CH2-CH2-)n
- D. (-CF2-CH2-)n
Explanation: Teflon is a synthetic polymer containing carbon and fluorine called polytetrafluoroethylene. Its formula is (C2F4)n.
Correct answer: (-CF2-CF2-)n