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What role does carbonic acid play in the human body?
- A. Digests food
- B. Kills viruses
- C. Maintains pH of blood
- D. Grows hair
Correct Answer: C
Rationale: In the human body, carbonic acid, formed when carbon dioxide dissolves in water, plays a crucial role in maintaining the pH balance of blood. It acts as a buffer system, responsible for regulating blood acidity levels and preventing significant pH fluctuations that could harm the body. Choices A, B, and D are inaccurate as they do not reflect the actual function of carbonic acid in the human body.
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Chemical reactions in living systems proceed along catabolic pathways, leading to an increase in which of the following?
- A. Entropy
- B. Enthalpy
- C. Glucose
- D. Glycogen
Correct Answer: A
Rationale: In catabolic pathways, complex molecules are broken down into simpler ones, releasing energy. This process increases entropy, which is a measure of disorder or randomness in a system. As molecules are broken down, they become more disordered, causing an increase in entropy. Therefore, the correct answer is 'Entropy.' Enthalpy refers to the total heat content of a system, glucose and glycogen are specific molecules and not directly related to the increase in disorder during catabolic reactions.
Which subatomic particle can always be used to identify an atom?
- A. Protons
- B. Neutrons
- C. Electrons
- D. None of the above
Correct Answer: A
Rationale: The correct answer is A: Protons. Protons are positively charged subatomic particles found in the nucleus of an atom. The number of protons in an atom's nucleus determines the element's identity. While neutrons and electrons are also essential components of an atom, it is the number of protons that uniquely identifies the element. Therefore, protons can always be used to identify an atom.
Which of the following describes atomic mass?
- A. Mass of protons and electrons
- B. Mass of neutrons and electrons
- C. Average mass of that element's isotopes
- D. Number of moles in a solution
Correct Answer: C
Rationale: The correct answer is C: Average mass of that element's isotopes. Atomic mass is the weighted average mass of the isotopes of an element, considering the natural abundance of each isotope. It is not just the sum of protons and neutrons or neutrons and electrons. Understanding atomic mass is crucial in chemistry as it helps in determining the molar mass of elements, which is essential in various chemical calculations such as stoichiometry and reaction equations.
What is the mass of ethyl alcohol that exactly fills a 200.0 mL container?
- A. 157.8 g
- B. 253.49 g
- C. 0.0039 g
- D. None of the above
Correct Answer: A
Rationale: To determine the mass of ethyl alcohol that fills a 200.0 mL container, we use the formula: Mass = Volume x Density. Given that the density of ethyl alcohol is 0.789 g/mL, multiplying the volume (200.0 mL) by the density gives us 200.0 mL x 0.789 g/mL = 157.8 g. Therefore, the correct answer is A, 157.8 g, representing the mass of ethyl alcohol that exactly fills the 200.0 mL container.
What is the name for a reaction in which electrons are transferred from one atom to another?
- A. combustion reaction
- B. synthesis reaction
- C. redox reaction
- D. double-displacement reaction
Correct Answer: C
Rationale: A redox reaction, also known as a reduction-oxidation reaction, involves the transfer of electrons from one substance to another. During this process, one substance is oxidized (loses electrons) while another is reduced (gains electrons). This transfer of electrons is a key characteristic of redox reactions, making choice C the correct answer. Combustion reaction (choice A) involves a substance reacting with oxygen to produce heat and light, but it does not necessarily involve electron transfer. Synthesis reaction (choice B) involves the combination of two or more substances to form a new compound, without necessarily involving electron transfer. Double-displacement reaction (choice D) involves the exchange of ions between two compounds, but not the transfer of electrons from one atom to another.