Nokea
What property of a substance measures the amount of matter per unit volume?
- A. Mass
- B. Weight
- C. Density
- D. Volume
Correct Answer: C
Rationale: Density is the property of a substance that measures the amount of matter per unit volume. It is calculated by dividing the mass of an object by its volume. Mass refers to the amount of matter in an object, weight is the force of gravity acting on an object, and volume is the amount of space an object occupies. Therefore, in this context, density is the correct answer as it specifically relates to the concentration of matter within a given volume.
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Which group of elements is known for their reactivity and ability to form strong bonds with other elements?
- A. Noble gases
- B. Halogens
- C. Alkali metals
- D. Transition metals
Correct Answer: B
Rationale: Halogens are a group of elements in the periodic table known for their high reactivity and ability to form strong bonds with other elements. They possess seven valence electrons, requiring only one more electron to achieve a stable electron configuration, making them highly reactive. Halogens readily form compounds with other elements by gaining an electron to achieve a full outer shell, resulting in the formation of strong covalent bonds. Noble gases (option A), on the other hand, are known for their inertness and stable electron configurations, making them unlikely to form bonds. Alkali metals (option C) are highly reactive but do not form bonds as strong as halogens. Transition metals (option D) are recognized for their variable oxidation states and ability to create complex ions but are not as reactive as halogens when it comes to bond formation.
Which type of reaction is represented by the equation A + B → AB?
- A. Synthesis
- B. Decomposition
- C. Single Replacement
- D. Double Replacement
Correct Answer: A
Rationale: The correct answer is 'Synthesis.' In a synthesis reaction, two or more reactants combine to form a single product. The equation A + B → AB represents a synthesis reaction where substances A and B combine to form compound AB. Choice B, 'Decomposition,' involves a single compound breaking down into two or more simpler substances, which is not the case in this equation. Choices C and D, 'Single Replacement' and 'Double Replacement,' involve the replacement of elements in compounds or the exchange of ions between compounds, neither of which is depicted in the given equation. Thus, 'Synthesis' is the most suitable classification for the reaction A + B → AB.
What is the primary function of the myelin sheath that surrounds some axons in the nervous system?
- A. To initiate nerve impulses
- B. To transmit sensory information
- C. To speed up the transmission of nerve impulses
- D. To connect neurons at synapses
Correct Answer: C
Rationale: The primary function of the myelin sheath is to speed up the transmission of nerve impulses. The myelin sheath acts as an insulating layer around the axon, allowing for faster conduction of electrical impulses along the nerve fiber. This insulation prevents the electrical signal from dissipating or 'leaking' out, which helps in the rapid and efficient transmission of nerve impulses along the axon. Choice A is incorrect because the myelin sheath does not initiate nerve impulses; it helps in conducting them. Choice B is incorrect as the myelin sheath's main role is not in transmitting sensory information but rather in facilitating the transmission of nerve impulses. Choice D is incorrect because the myelin sheath's function is not to connect neurons at synapses; instead, it is primarily involved in enhancing the speed of nerve impulse transmission.
Which of the following substances is an example of an acidic gas?
- A. Nitrogen (Nâ‚‚)
- B. Carbon dioxide (COâ‚‚)
- C. Sulfur dioxide (SOâ‚‚)
- D. Oxygen (Oâ‚‚)
Correct Answer: C
Rationale: The correct answer is C, Sulfur dioxide (SOâ‚‚). Sulfur dioxide is an acidic gas because when dissolved in water, it forms sulfurous acid, which imparts acidic properties. Nitrogen (Nâ‚‚), carbon dioxide (COâ‚‚), and oxygen (Oâ‚‚) are not considered acidic gases. Nitrogen is a neutral gas, carbon dioxide forms a weakly acidic solution when dissolved in water, and oxygen is a neutral gas.
What is the process of converting lactic acid back into pyruvate called?
- A. Glycolysis
- B. Gluconeogenesis
- C. Cori cycle
- D. Oxidative phosphorylation
Correct Answer: C
Rationale: A) Glycolysis is the process of breaking down glucose into pyruvate.
B) Gluconeogenesis is the process of synthesizing glucose from non-carbohydrate sources.
C) The Cori cycle is the process by which lactic acid produced by anaerobic metabolism in muscles is transported to the liver and converted back into glucose or pyruvate.
D) Oxidative phosphorylation is the process by which ATP is synthesized using energy derived from the transfer of electrons in the electron transport chain.