HESI A2
HESI A2 Chemistry
1. Which of these intermolecular forces would result in the lowest boiling point?
- A. Dipole-dipole interaction
- B. London dispersion force
- C. Keesom interaction
- D. Hydrogen bonding
Correct answer: B
Rationale: The London dispersion force is the weakest intermolecular force among the options provided. These forces are present in all molecules and are caused by temporary fluctuations in electron density, resulting in temporary dipoles. Since London dispersion forces are generally weaker than dipole-dipole interactions, Keesom interactions, and hydrogen bonding, a substance with London dispersion forces as the primary intermolecular force would have the lowest boiling point due to the weaker intermolecular forces holding the molecules together. Dipole-dipole interactions, Keesom interactions, and hydrogen bonding are stronger intermolecular forces compared to London dispersion forces, resulting in higher boiling points for substances that exhibit these interactions.
2. What is the best description for the term flaccid?
- A. Light-colored
- B. Drooping or loose
- C. Uncontaminated
- D. Unusually aggressive
Correct answer: B
Rationale: The term 'flaccid' is commonly used to describe something that is limp, soft, or lacking firmness. It suggests a lack of stiffness or rigidity, often used to describe plants, muscles, or other objects that are in a drooping or loose state. Choice A 'Light-colored' is incorrect as it does not convey the meaning of flaccid. Choice C 'Uncontaminated' and Choice D 'Unusually aggressive' are also incorrect as they do not relate to the definition of flaccid.
3. Choose the meaning of the word 'disregard' in the following sentence: 'He chose to disregard the warnings.'
- A. Have no opinion about
- B. Pay attention to
- C. Care for
- D. Ignore
Correct answer: D
Rationale: The correct meaning of 'disregard' in the sentence provided is 'to ignore.' When someone disregards something, they are choosing not to pay attention to it or consider it important. Choice A, 'Have no opinion about,' is incorrect as disregard implies actively ignoring something rather than having no opinion. Choice B, 'Pay attention to,' is the opposite of disregard. Choice C, 'Care for,' is also the opposite of disregard, as caring for something implies giving it importance and attention.
4. Which one of the following best describes the function of a cell membrane?
- A. It controls the substances entering and leaving the cell.
- B. It maintains the cell's shape.
- C. It controls the substances entering the cell.
- D. It supports the cell's structures.
Correct answer: A
Rationale: The correct answer is A. The function of a cell membrane is to control the substances entering and leaving the cell. The cell membrane is selectively permeable, allowing it to regulate the movement of ions and molecules in and out of the cell to maintain internal balance and proper function. Choice B is incorrect because while the cell membrane does provide some structural support, its primary function is not to maintain the cell's shape. Choice C is incorrect because the cell membrane controls both the substances entering and leaving the cell, not just those entering. Choice D is incorrect as the primary function of the cell membrane is not to support the cell's structures but to regulate the movement of substances.
5. What kind of symbiosis exists between a pneumonia bacterium and a human?
- A. Mutualism
- B. Parasitism
- C. Commensalism
- D. Competition
Correct answer: B
Rationale: In the case of a pneumonia bacterium and a human, the relationship is best described as parasitism. The bacterium benefits by causing harm to the human host, while the human is negatively affected by the presence of the bacterium, leading to illness or infection. This is a classic example of a parasitic relationship where one organism benefits at the expense of the other. Mutualism (Choice A) is a type of symbiotic relationship where both organisms benefit from each other. Commensalism (Choice C) is a symbiotic relationship where one organism benefits, and the other is neither helped nor harmed. Competition (Choice D) refers to a relationship where both organisms are negatively affected by each other as they compete for resources.
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