HESI A2
Chemistry HESI A2 Practice Test
1. What is the charge of an alpha particle?
- A. -1
- B. +1
- C. +2
- D. No charge
Correct answer: C
Rationale: An alpha particle consists of two protons and two neutrons, resulting in a total charge of +2 due to the presence of two positively charged protons. Therefore, the correct answer is C, indicating a charge of +2. Choices A, B, and D are incorrect because an alpha particle is positively charged due to the two protons it contains, resulting in a charge of +2.
2. To the nearest whole number, what is the mass of one mole of water?
- A. 16 g/mol
- B. 18 g/mol
- C. 20 g/mol
- D. 22 g/mol
Correct answer: B
Rationale: The molar mass of water (Hâ‚‚O) is calculated by adding the atomic masses of two hydrogen atoms (each with a molar mass of approximately 1 g/mol) and one oxygen atom (with a molar mass of approximately 16 g/mol). Therefore, the molar mass of water is approximately 18 g/mol, making choice B the correct answer. Choice A (16 g/mol) is incorrect because it represents the molar mass of oxygen, not water. Choices C (20 g/mol) and D (22 g/mol) are incorrect as they do not correspond to the molar mass of water.
3. What is the oxidation state of the potassium ion in the compound KCl?
- A. +1
- B. -1
- C. +2
- D. -2
Correct answer: A
Rationale: In the compound KCl (potassium chloride), potassium is in Group 1 of the periodic table, which means it has a valence electron of 1. Chlorine is in Group 17 and gains one electron to achieve a stable electron configuration by forming an ionic bond with potassium. As a result, the potassium ion in KCl has a +1 oxidation state. Therefore, the correct answer is +1. Choices B, C, and D are incorrect as they do not reflect the oxidation state of the potassium ion in KCl.
4. Which material has the smallest specific heat capacity?
- A. water
- B. wood
- C. aluminum
- D. glass
Correct answer: C
Rationale: Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. Among the options provided, aluminum has the smallest specific heat capacity. This means that it requires the least amount of heat to raise its temperature compared to water, wood, and glass. Water has a high specific heat capacity, making it resistant to temperature changes, while wood and glass have higher specific heat capacities compared to aluminum.
5. What is the charge of noble gases?
- A. -1
- B. 0
- C. 1
- D. 2
Correct answer: B
Rationale: The correct answer is B: 0. Noble gases have a charge of 0 because they have full valence shells and are inert. This makes them stable and unreactive, resulting in a charge of 0 as they do not readily gain or lose electrons. Choices A, C, and D are incorrect because noble gases do not typically form ions by gaining or losing electrons, so they do not carry a charge of -1, 1, or 2.
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