Nokea
How does the Law of Conservation of Mass apply to this reaction: 2H₂ + O₂ → 2H₂O?
- A. Electrons are not lost.
- B. The hydrogen does not lose mass.
- C. New water molecules are formed.
- D. There is no decrease or increase in matter.
Correct Answer: D
Rationale: The Law of Conservation of Mass states that matter cannot be created or destroyed in a chemical reaction. In the given reaction, 2 moles of hydrogen combine with 1 mole of oxygen to form 2 moles of water. The total mass of the reactants (hydrogen and oxygen) is equal to the total mass of the products (water), meaning there is no decrease or increase in matter. The total mass of the system remains constant, demonstrating the conservation of mass. Choices A, B, and C are incorrect because the conservation of mass does not specifically relate to electrons, individual elements (like hydrogen), or the formation of new molecules; instead, it focuses on the overall mass of the system before and after the reaction.
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A rock has a mass of 3 grams (g) and a volume of 4 cm³. What is its density?
- A. 8.90 g/cm³
- B. 0.38 g/cm³
- C. 77.22 g/cm³
- D. 2.65 g/cm³
Correct Answer: D
Rationale: Density is determined by the formula Density = Mass / Volume. For this rock, the mass is 3g, and the volume is 4 cm³. Applying the formula: Density = 3g / 4cm³ = 0.75 g/cm³. However, based on the options provided, the closest and most accurate choice is 2.65 g/cm³, corresponding to option D. Choice A, 8.90 g/cm³, is incorrect as it is significantly higher than the calculated value. Choice B, 0.38 g/cm³, and Choice C, 77.22 g/cm³, are also incorrect and do not match the correct calculation.
What is an isotope? For any given element, it is an atom with which of the following?
- A. a different atomic number
- B. a different number of protons
- C. a different number of electrons
- D. a different mass number
Correct Answer: D
Rationale: An isotope of an element is an atom with a different number of neutrons, resulting in a different mass number. Isotopes of the same element have the same number of protons (which determines the element's identity) but differ in the number of neutrons, leading to variations in mass numbers. Choice A is incorrect because isotopes of the same element have the same atomic number. Choice B is incorrect because isotopes of the same element have the same number of protons. Choice C is incorrect because isotopes of the same element have the same number of electrons.
What is the dermis composed of?
- A. Adipose tissue
- B. Epithelial cells
- C. Connective tissue
- D. Muscle tissue
Correct Answer: C
Rationale: The correct answer is C: Connective tissue. The dermis is primarily composed of connective tissue, which includes collagen and elastin fibers that provide strength and elasticity to the skin. It houses blood vessels, nerve endings, hair follicles, and glands, playing a crucial role in supporting the skin structure and function. Adipose tissue (choice A) is found in the subcutaneous layer beneath the dermis, providing insulation and energy storage. Epithelial cells (choice B) form the outermost layer of the skin called the epidermis. Muscle tissue (choice D) is not a significant component of the dermis but is found deeper in the body associated with movement and support.
What is the path of oxygenated blood flow in our body?
- A. From the heart directly to the brain
- B. From the lungs to the left atrium, then to the left ventricle, and out through the aorta
- C. From the body to the right atrium to the lungs
- D. From the left atrium directly to the aorta
Correct Answer: B
Rationale: Oxygenated blood flows from the lungs to the left atrium, then to the left ventricle, and is pumped out through the aorta to the body. This pathway ensures efficient oxygen delivery to the body's tissues and organs. Choice A is incorrect as oxygenated blood does not flow directly from the heart to the brain. Choice C is incorrect as it suggests a route from the body to the right atrium and then to the lungs, which is the pathway for deoxygenated blood. Choice D is incorrect as it describes a direct pathway from the left atrium to the aorta, skipping the left ventricle, which is essential for pumping blood to the body.
What macromolecules are formed from amino acids, and what are their roles?
- A. Lipids; store energy
- B. Carbohydrates; provide energy
- C. Proteins; perform various functions like catalysis, transport, and structural support
- D. Nucleic acids; store genetic information
Correct Answer: C
Rationale: The correct answer is C. Proteins are macromolecules formed from amino acids and have diverse roles, such as serving as enzymes, transport molecules, and providing structural support. They are essential for catalysis, cellular communication, immune response, and many other functions in living organisms. Choices A, B, and D are incorrect. Lipids are not formed from amino acids but from fatty acids and glycerol, mainly serving as energy storage molecules. Carbohydrates are composed of sugars and provide energy to the body. Nucleic acids, like DNA and RNA, are made up of nucleotides and store genetic information in cells.