Nokea
What is the pH of a solution with a hydrogen ion concentration of (1x10^{-9}) M?
- A. 5
- B. 7
- C. 9
- D. 11
Correct Answer: C
Rationale: The pH of a solution can be calculated using the formula: pH = -log[H+]. Given that the hydrogen ion concentration is \(1 \times 10^{-9}\) M, the pH can be calculated as pH = -log(1 x 10^-9) = 9. Therefore, the correct answer is C) 9.
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How is the density of a substance calculated?
- A. Mass / Volume
- B. Volume / Mass
- C. Mass x Volume
- D. None of the above
Correct Answer: A
Rationale: The density of a substance is calculated by dividing the mass of the substance by its volume. The formula for density is Density = Mass / Volume. This calculation allows us to determine how much mass is present in a given volume of a substance, making option A the correct choice. Choice B (Volume / Mass) is incorrect because density is defined as mass per unit volume, so mass should be the numerator. Choice C (Mass x Volume) is incorrect as this would result in a different unit of measurement and not represent density. Choice D (None of the above) is incorrect as there is a specific formula for calculating density, which is mass divided by volume.
What is the relationship between mass and weight on Earth's surface?
- A. Mass and weight are equal
- B. Mass is greater than weight
- C. Weight is greater than mass
- D. Mass and weight are not related
Correct Answer: C
Rationale: The correct answer is C: Weight is greater than mass. Mass is a measure of the amount of matter in an object, while weight is the force of gravity acting on that object. On Earth's surface, weight is greater than mass because gravity pulls objects towards the center of the Earth, resulting in a force that we perceive as weight. Choice A is incorrect because mass and weight are not equal; weight is a force, while mass is a measure of the amount of matter. Choice B is incorrect because mass is not greater than weight; weight is the force exerted due to gravity. Choice D is incorrect as mass and weight are related; weight is dependent on mass and the gravitational force acting on the object.
Which type of energy is associated with the random motion of particles in a substance?
- A. Potential energy
- B. Mechanical energy
- C. Thermal energy
- D. Chemical energy
Correct Answer: C
Rationale: Thermal energy is the correct answer as it is associated with the random motion of particles in a substance. When particles move randomly, they generate heat energy, which is a form of thermal energy. Potential energy is stored energy that can be converted into other forms when released, such as kinetic energy. Mechanical energy is the sum of potential and kinetic energy in an object, which is not directly related to the random motion of particles. Chemical energy is energy stored in the bonds of chemical compounds and is not specifically related to the motion of particles.
Antibodies, crucial for immune defense, are produced by:
- A. Neutrophils
- B. Lymphocytes
- C. Monocytes
- D. Basophils
Correct Answer: B
Rationale: Antibodies are produced by a specific type of lymphocyte known as B cells. B cells are a critical component of the adaptive immune system and are responsible for producing antibodies in response to pathogens. Neutrophils, monocytes, and basophils are types of white blood cells that are part of the innate immune response and do not have the function of producing antibodies. Neutrophils are primarily involved in phagocytosis, monocytes differentiate into macrophages and dendritic cells for antigen presentation, while basophils are involved in allergic reactions and parasitic infections.
What is the name for the hard, protective protein that makes up hair and nails?
- A. Collagen
- B. Keratin
- C. Elastin
- D. Fibrin
Correct Answer: B
Rationale: Keratin is the correct answer as it is the hard, protective protein that comprises hair and nails. Collagen is a different type of protein found in connective tissues, providing structure and support. Elastin imparts elasticity to tissues, allowing them to stretch and recoil. Fibrin is a protein involved in the blood clotting process and is not related to the structure of hair and nails. Therefore, choices A, C, and D are incorrect in the context of the question.