balance this equation fe cl fecl 2 3

HESI A2

HESI A2 Chemistry Practice Questions

1. Balance this equation: Fe + Cl2 â†’ FeCl3

A. 2Fe + 2Cl2 â†’ 2FeCl3
B. 2Fe + 3Cl2 â†’ 2FeCl3
C. 3Fe + 2Cl2 â†’ 3FeCl3
D. 3Fe + 3Cl2 â†’ 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 â†’ 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.

2. What is the mass number of an atom with 6 protons, 6 neutrons, and 6 electrons?

A. 12
B. 18
C. 6
D. 8

Correct answer: A

Rationale: The mass number of an atom is the sum of protons and neutrons. In this case, the atom has 6 protons and 6 neutrons, thus the mass number is 6 + 6 = 12. Therefore, choice A (12) is the correct answer. Choices B (18), C (6), and D (8) are incorrect because the mass number is determined by the sum of protons and neutrons, not the number of electrons or a different combination of particles.

3. What is the term used when an atom gains one or more electrons?

A. Cation
B. Anion
C. Isotope
D. Electron

Correct answer: B

Rationale: When an atom gains electrons, it becomes negatively charged and is called an anion. An anion is formed when an atom gains one or more electrons, leading to an excess of negative charge. Choice A, 'Cation,' is incorrect because a cation is formed when an atom loses electrons, resulting in a positively charged ion. Choice C, 'Isotope,' refers to atoms of the same element with different numbers of neutrons and is not related to gaining electrons. Choice D, 'Electron,' is the particle that an atom gains to become an anion, not the term for the atom itself after gaining electrons.

4. What charge do alpha radiation particles have?

A. -2
B. 0
C. +2
D. +1

Correct answer: C

Rationale: The correct answer is C: +2. Alpha radiation particles consist of two protons and two neutrons, giving them a net charge of +2. This positive charge is due to the presence of the two protons in the nucleus of the alpha particle. Choice A (-2) is incorrect as alpha particles have a positive charge. Choice B (0) is incorrect as alpha particles carry a charge. Choice D (+1) is incorrect as alpha particles have a higher positive charge due to the presence of two protons.

5. If oxygen is in a compound, what would its oxidation number be?

A. 2
B. -2
C. 0
D. -1

Correct answer: B

Rationale: Oxygen typically has an oxidation number of -2 in compounds because it tends to gain electrons. This is due to its high electronegativity, which leads to oxygen attracting electrons towards itself in a chemical bond. Choice A (2) is incorrect because oxygen doesn't have a +2 oxidation number in compounds. Choice C (0) is incorrect as oxygen rarely has an oxidation number of 0 in compounds. Choice D (-1) is incorrect as oxygen's oxidation number in compounds is typically -2, not -1.