Nokea
Antigen-antibody binding is the principle behind:
- A. Vaccination
- B. Disinfection
- C. Sterilization
- D. Antibiotic resistance
Correct Answer: A
Rationale: Antigen-antibody binding is the principle behind vaccination. When a vaccine containing antigens (weakened or killed pathogens) is introduced into the body, the immune system produces antibodies that bind to these antigens. This binding triggers an immune response, leading to the production of memory cells that provide immunity against future infections by the same pathogen. Vaccination helps the body develop immunity without causing the disease itself, thereby protecting individuals from infectious diseases. Disinfection and sterilization involve different processes to eliminate or reduce pathogens on surfaces or objects. Antibiotic resistance is a phenomenon where bacteria evolve to resist the effects of antibiotics and is not directly related to antigen-antibody binding.
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What happens to the kinetic energy of an object when its velocity is doubled?
- A. Kinetic energy remains the same
- B. Kinetic energy is halved
- C. Kinetic energy doubles
- D. Kinetic energy quadruples
Correct Answer: C
Rationale: Kinetic energy is directly proportional to the square of the velocity of an object according to the kinetic energy formula (KE = 0.5 * m * v^2). When the velocity is doubled, the kinetic energy increases by a factor of four (2^2), which means it doubles. Therefore, when the velocity of an object is doubled, its kinetic energy also doubles. Choice A is incorrect because kinetic energy is not constant but dependent on velocity. Choice B is incorrect because halving the velocity would result in 1/4 of the original kinetic energy. Choice D is incorrect as quadrupling the kinetic energy would occur if the velocity is squared, not the kinetic energy.
What property of a wave determines the loudness of sound when heard by the human ear?
- A. Frequency
- B. Amplitude
- C. Wavelength
- D. Velocity
Correct Answer: B
Rationale: The amplitude of a wave determines the loudness of sound when heard by the human ear. The greater the amplitude of a sound wave, the louder the sound will be perceived. Frequency (Choice A) refers to the number of wave cycles in a given time period. Wavelength (Choice C) is the distance between two corresponding points on a wave. Velocity (Choice D) is the speed at which the wave travels and does not directly affect the loudness of sound perceived by the human ear.
What is the difference between mitosis and meiosis?
- A. Mitosis produces haploid cells, while meiosis produces diploid cells
- B. Mitosis involves crossing over, while meiosis does not.
- C. Mitosis results in four daughter cells, while meiosis results in two
- D. Mitosis is responsible for sexual reproduction, while meiosis is responsible for asexual reproduction.
Correct Answer: C
Rationale: - Mitosis is a type of cell division that results in two identical daughter cells with the same number of chromosomes as the parent cell. Therefore, mitosis results in two daughter cells.
- Meiosis is a type of cell division that results in four daughter cells, each with half the number of chromosomes as the parent cell. This reduction in chromosome number is essential for sexual reproduction.
- Option A is incorrect because mitosis produces diploid cells (cells with the same number of chromosomes as the parent cell), while meiosis produces haploid cells (cells with half the number of chromosomes as the parent cell).
- Option B is incorrect because crossing over, the exchange of genetic material between homologous chromosomes, occurs during meiosis and not during mitosis.
- Option D is incorrect because mitosis is not responsible for sexual reproduction; it is a process of asexual reproduction and
In the reaction 2H2 + O2 → 2H2O, how many moles of oxygen are required to react completely with 4 moles of hydrogen?
- A. 1
- B. 2
- C. 3
- D. 4
Correct Answer: B
Rationale: The balanced chemical equation indicates that 2 moles of H2 react with 1 mole of O2 to produce 2 moles of H2O. To determine how many moles of O2 are required to react with 4 moles of H2, you can use the mole ratio from the balanced equation: 2 moles of H2 react with 1 mole of O2. Therefore, to react completely with 4 moles of H2, you would need 2 moles of O2 (4 moles H2 · 2 moles H2 per 1 mole O2). Hence, 2 moles of oxygen are required to react completely with 4 moles of hydrogen. Choices A, C, and D are incorrect because they do not reflect the correct stoichiometry as defined by the balanced chemical equation.
Which of the following is an example of an aromatic compound?
- A. Ethanol
- B. Toluene
- C. Acetone
- D. Butanal
Correct Answer: B
Rationale: Toluene is an aromatic compound due to its benzene ring structure, which satisfies the criteria of aromaticity. Aromatic compounds contain conjugated pi electrons in a ring structure, providing extra stability. Ethanol, acetone, and butanal are not aromatic compounds as they do not possess a benzene ring or meet the aromaticity criteria. Ethanol is an alcohol, acetone is a ketone, and butanal is an aldehyde, none of which have the characteristic benzene ring structure of aromatic compounds.