HESI A2
HESI A2 Chemistry Practice Test
1. What type of starch is glycogen?
- A. Plant starch
- B. Animal starch
- C. Glucose
- D. Cellulose
Correct answer: B
Rationale: Glycogen is classified as animal starch, not plant starch. It is the storage form of glucose in animals, primarily found in the liver and muscles. Choice A (Plant starch) is incorrect because glycogen is not derived from plants. Choice C (Glucose) is incorrect as glucose is a monosaccharide and not a type of starch. Choice D (Cellulose) is incorrect as cellulose is a structural polysaccharide found in plant cell walls, not the same as glycogen.
2. Which, if any, of the following statements is false?
- A. In an endothermic process, solubility typically decreases with an increase in temperature and increases if the temperature decreases
- B. In an exothermic process, solubility decreases with an increase in temperature
- C. All of the Above
- D. None of the Above
Correct answer: A
Rationale: Statement A is false. In an endothermic process, solubility typically decreases with an increase in temperature and increases if the temperature decreases. When heat is added to an endothermic process, it disrupts the intermolecular forces holding the solute particles together, making them more likely to dissolve. Therefore, higher temperatures generally lead to increased solubility in an endothermic process. Statement B is correct as in an exothermic process, solubility usually decreases with an increase in temperature due to the excess heat causing solute particles to come out of solution. As Statements A and B are contradictory, the answer cannot be 'All of the Above' or 'None of the Above.'
3. One factor that affects rates of reaction is concentration. Which of these statements about concentration is/are correct?
- A. A higher concentration of reactants causes more effective collisions per unit time, leading to an increased reaction rate
- B. A lower concentration of reactants causes fewer effective collisions per unit time, leading to a decreased reaction rate
- C. A higher concentration of reactants causes more effective collisions per unit time, leading to a decreased reaction rate
- D. A higher concentration of reactants causes fewer effective collisions per unit time, leading to an increased reaction rate
Correct answer: A
Rationale: A higher concentration of reactants causes more effective collisions per unit time, leading to an increased reaction rate. This is because a higher concentration means there are more reactant molecules in a given volume, increasing the likelihood of collisions between them. With more collisions occurring, there is a greater chance of successful collisions leading to the formation of products, hence increasing the reaction rate. Choice B is incorrect as a lower concentration decreases the number of collisions, reducing the reaction rate. Choice C is incorrect as a higher concentration increases collision frequency, which typically results in a higher reaction rate. Choice D is incorrect as a higher concentration usually leads to more collisions, thus increasing the reaction rate.
4. Which of the following is defined as the number of cycles of a wave that move past a fixed observation point per second?
- A. Wave
- B. Wavelength
- C. Frequency
- D. Wavefunction
Correct answer: C
Rationale: Frequency is defined as the number of cycles of a wave that pass a fixed observation point per second. It is a fundamental characteristic of a wave and is measured in Hertz (Hz). The frequency of a wave determines its pitch in the case of sound waves and its color in the case of light waves. Choice A, 'Wave,' is incorrect because a wave refers to the disturbance or oscillation that travels through a medium. Choice B, 'Wavelength,' is incorrect as it represents the distance between two corresponding points on a wave (e.g., crest to crest). Choice D, 'Wavefunction,' is not the correct answer as it is a mathematical function used in quantum mechanics to describe the behavior of particles and systems.
5. Under which of the following conditions do real gases approach ideal behavior?
- A. At high pressure and high temperature
- B. At low pressure and high temperature
- C. Near the boiling point of water
- D. Real gases can never exhibit ideal behavior
Correct answer: A
Rationale: Real gases approach ideal behavior at high pressure and high temperature. At these conditions, the volume of the gas molecules becomes negligible compared to the total volume of the gas. Additionally, the average distance between molecules becomes small enough for intermolecular forces to become less significant, leading to behavior that closely mirrors the assumptions of the ideal gas law. Choice B is incorrect because low pressure does not favor ideal behavior as the volume of gas molecules becomes more significant. Choice C is incorrect as the boiling point of water does not directly relate to ideal gas behavior. Choice D is incorrect because real gases can approach ideal behavior under specific conditions, such as high pressure and high temperature.
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