HESI A2
Chemistry HESI A2 Quizlet
1. Which of the following types of matter changes in volume with changes in temperature and pressure?
- A. Liquid
- B. Gas
- C. Solid
- D. Plasma
Correct answer: B
Rationale: A gas changes its volume with changes in temperature and pressure due to the particles moving more rapidly at higher temperatures, and pressure affects the space between particles. Liquids have a relatively fixed volume but take the shape of their container. Solids have a definite shape and volume, so they do not change volume with changes in temperature and pressure. Plasma is a state of matter where particles are highly energized and do not have a fixed volume, but it does not exhibit volume changes with temperature and pressure variations.
2. Balance this equation: Fe + Cl2 → FeCl3
- A. 2Fe + 2Cl2 → 2FeCl3
- B. 2Fe + 3Cl2 → 2FeCl3
- C. 3Fe + 2Cl2 → 3FeCl3
- D. 3Fe + 3Cl2 → 6FeCl3
Correct answer: B
Rationale: In the given equation, Fe combines with Cl to form FeCl3. To balance the equation, we need to have the same number of each element on both sides. Since Cl is represented as Cl2 in the equation, we need 3 Cl2 molecules to balance Fe, resulting in 2Fe + 3Cl2 → 2FeCl3. Choice A is incorrect because it only balances Fe but not Cl2. Choice C is incorrect as it balances Fe but not Cl2. Choice D is incorrect as it balances Fe but overbalances Cl2.
3. Which number represents the number of protons in an element?
- A. Atomic mass
- B. Mass number
- C. Atomic number
- D. Proton number
Correct answer: C
Rationale: The correct answer is C: Atomic number. The atomic number corresponds to the number of protons in an element. Protons are positively charged subatomic particles found in the nucleus of an atom. Each element has a unique atomic number, which defines its identity based on the number of protons it contains. Choice A, Atomic mass, is incorrect as it refers to the average mass of an atom of an element. Choice B, Mass number, represents the total number of protons and neutrons in an atom's nucleus. Choice D, Proton number, is not a commonly used term in chemistry to indicate the number of protons.
4. How many electron pairs are shared to form a triple covalent bond?
- A. 1
- B. 2
- C. 3
- D. 4
Correct answer: C
Rationale: The correct answer is C. In a triple covalent bond, three pairs of electrons are shared between two atoms. This sharing results in a total of six electrons being shared, making the bond strong. Choice A (1) is incorrect because a single covalent bond involves the sharing of one pair of electrons. Choice B (2) is incorrect as a double covalent bond consists of the sharing of two pairs of electrons. Choice D (4) is incorrect because there are only three pairs of electrons shared in a triple covalent bond, not four.
5. How many electrons are in a neutral atom of neon?
- A. 9
- B. 10
- C. 11
- D. 12
Correct answer: B
Rationale: The atomic number of neon is 10, which represents the number of protons in its nucleus. In a neutral atom, the number of electrons is equal to the number of protons to maintain electrical neutrality. Therefore, a neutral atom of neon contains 10 electrons, matching the 10 protons within the nucleus. Choice A (9 electrons) is incorrect as it doesn't correspond to the atomic number of neon. Choices C (11 electrons) and D (12 electrons) are also incorrect as they do not align with the correct atomic number of neon.
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