HESI A2
HESI A2 Chemistry Questions
1. What is the name of the process by which a gas turns into a liquid?
- A. Sublimation
- B. Condensation
- C. Evaporation
- D. Deposition
Correct answer: B
Rationale: The correct answer is B: Condensation. Condensation is the process where gas transforms into a liquid. When gas cools down, it loses energy and its particles come closer, leading to the formation of liquid droplets. Sublimation is the direct transition from solid to gas without passing through the liquid state. Evaporation is the process of liquid turning into a gas, and deposition is the transition of gas directly into a solid. Therefore, choices A, C, and D are incorrect as they describe different phase transitions.
2. Which element has an atomic mass greater than that of sodium?
- A. Boron
- B. Oxygen
- C. Fluorine
- D. Silicon
Correct answer: D
Rationale: Silicon has an atomic mass greater than that of sodium. The atomic mass of silicon is approximately 28.0855 u, whereas the atomic mass of sodium is approximately 22.9898 u. Therefore, silicon has a greater atomic mass compared to sodium. Boron, Oxygen, and Fluorine have atomic masses lower than sodium, making them incorrect choices in this context.
3. If electrons are not shared equally in a covalent bond, the bond is what?
- A. Polar
- B. Non-polar
- C. Ionic
- D. Hydrogen
Correct answer: A
Rationale: A polar covalent bond occurs when electrons are shared unequally between atoms. In this type of bond, one atom has a stronger pull on the shared electrons, leading to a partial positive and partial negative charge distribution within the molecule. Choice B, non-polar, is incorrect because in non-polar covalent bonds, electrons are shared equally between atoms. Choice C, ionic, is incorrect as ionic bonds involve a transfer of electrons rather than sharing. Choice D, hydrogen, is incorrect as it does not describe the nature of a covalent bond.
4. What is a benefit of water's ability to make hydrogen bonds?
- A. Lack of cohesiveness
- B. Low surface tension
- C. Use as a nonpolar solvent
- D. High specific heat
Correct answer: D
Rationale: The correct answer is D, high specific heat. Water's ability to form hydrogen bonds results in a high specific heat capacity, allowing it to absorb and release a large amount of heat energy with minimal temperature change. This property is essential for moderating temperature changes in organisms and maintaining stable environmental conditions for life processes. Choices A, lack of cohesiveness, and C, use as a nonpolar solvent, are incorrect. Water actually has high cohesiveness due to its ability to form hydrogen bonds, and it is a polar solvent, not nonpolar. Choice B, low surface tension, is also incorrect as water's hydrogen bonding contributes to its relatively high surface tension.
5. Which of the following elements is the most electronegative?
- A. Oxygen
- B. Fluorine
- C. Nitrogen
- D. Sodium
Correct answer: B
Rationale: Fluorine is the most electronegative element on the periodic table. It has the highest electronegativity value, indicating its strong ability to attract electrons in a chemical bond. This property makes it highly reactive, explaining why it is the correct answer in this question. Oxygen and Nitrogen are also electronegative elements, but they are not as electronegative as Fluorine. Sodium, on the other hand, is not electronegative; it is an electropositive element.
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