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. What is a mole?
- A. 6.02 x 10^23
- B. 1.00 x 10^24
- C. 6.02 x 10^22
- D. 6.02 x 10^25
Correct answer: A
Rationale: A mole is a unit used in chemistry to represent Avogadro's number, which is approximately 6.02 x 10^23. This number corresponds to the number of particles (atoms, molecules, ions) in one mole of a substance. Choice A, 6.02 x 10^23, is the correct answer as it accurately defines a mole. Choices B, C, and D provide values that are not equivalent to Avogadro's number, making them incorrect answers.
3. What is the oxidation state of the sulfur atom in sulfuric acid H2SO4?
- A. 4
- B. 6
- C. 8
- D. 10
Correct answer: B
Rationale: In sulfuric acid (H2SO4), sulfur has an oxidation state of +6. The oxidation state is determined by considering the overall charge of the compound and the known oxidation states of other elements. In this case, hydrogen is typically +1, and oxygen is -2. To balance the charges and match the compound's overall charge of 0, sulfur must have an oxidation state of +6. Choice A (4) is incorrect because it doesn't balance the charges in the compound. Choices C (8) and D (10) are also incorrect as they are not valid oxidation states for sulfur in this compound.
4. Among the following elements, which is a nonmetal?
- A. Mercury
- B. Magnesium
- C. Sulfur
- D. Potassium
Correct answer: C
Rationale: Sulfur is a nonmetal as it is located on the right side of the periodic table. Nonmetals generally exhibit properties such as being brittle, poor conductors of heat and electricity, and having lower melting points compared to metals. Mercury (A), Magnesium (B), and Potassium (D) are all metals due to their metallic properties. Mercury is a liquid metal at room temperature, Magnesium is a solid metal, and Potassium is a solid metal as well. Therefore, the correct answer is C, Sulfur.
5. What is the name of the group of elements that contains chlorine, fluorine, and iodine?
- A. Alkali metals
- B. Halogens
- C. Transition metals
- D. Noble gases
Correct answer: B
Rationale: The correct answer is 'Halogens.' Halogens are a group of elements that include chlorine, fluorine, and iodine. These elements are part of Group 17 in the periodic table. They share similar properties such as high reactivity and the ability to readily form compounds. Choice A, 'Alkali metals,' is incorrect as alkali metals are found in Group 1 of the periodic table, which includes elements like lithium and sodium. Choice C, 'Transition metals,' is incorrect as transition metals are located in the middle section of the periodic table, not in Group 17. Choice D, 'Noble gases,' is incorrect as noble gases are in Group 18 and include elements like helium and neon, which are chemically inert.
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