HESI A2
Chemistry HESI A2 Quizlet
1. What are the columns of the periodic table called?
- A. Periods
- B. Families
- C. Groups
- D. Rows
Correct answer: C
Rationale: In the periodic table, columns are referred to as groups, not periods, families, or rows. These groups share similar chemical properties due to the arrangement of elements within each group, which is based on the number of valence electrons. The vertical columns help classify elements with similar characteristics. Periods refer to the rows of the periodic table, while families or groups are the vertical columns.
2. 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.
3. What is stoichiometry?
- A. The study of energy changes in chemical reactions
- B. The study of the mass relationships in chemical reactions
- C. The study of atomic structure
- D. The study of molecular geometry
Correct answer: B
Rationale: Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. It focuses on the calculation of the amounts of substances consumed and produced in a reaction based on the balanced chemical equation. Choice A is incorrect because the study of energy changes in chemical reactions falls under thermodynamics. Choice C is incorrect as atomic structure is related to the arrangement of atoms within molecules. Choice D is incorrect as molecular geometry deals with the spatial arrangement of atoms within molecules.
4. 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.
5. Which of these represents a strong acid?
- A. CH₃COOH
- B. H₂SO₄
- C. NH₃
- D. KOH
Correct answer: B
Rationale: Among the options provided, H₂SO₄ (sulfuric acid) represents a strong acid. Strong acids completely ionize in water to produce a high concentration of H+ ions. Sulfuric acid is a strong acid known for its ability to dissociate almost completely in water, making it a strong acid. Choice A, CH₃COOH (acetic acid), is a weak acid that only partially dissociates in water. Choices C and D, NH₃ (ammonia) and KOH (potassium hydroxide), are bases and not acids.
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