HESI A2
Chemistry HESI A2 Practice Test
1. What is the correct name of AgNO₃?
- A. Argent nitrous
- B. Argent oxide
- C. Silver nitrite
- D. Silver nitrate
Correct answer: D
Rationale: The correct name for AgNO₃ is silver nitrate. In chemical nomenclature, the element symbol Ag represents silver, and the polyatomic ion NO₃ is known as nitrate. Therefore, when the silver ion (Ag⁺) combines with the nitrate ion (NO₃⁻), the resulting compound is named silver nitrate (AgNO₃). Choices A, B, and C are incorrect because they do not accurately represent the composition of AgNO₃. Argent nitrous (Choice A) and Argent oxide (Choice B) do not reflect the correct anion, and Silver nitrite (Choice C) uses a different anion altogether.
2. 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.
3. Al(NO3)3 + H2SO4 → Al2(SO4)3 + HNO3 is an example of which kind of reaction?
- A. Decomposition reaction
- B. Synthesis reaction
- C. Single replacement reaction
- D. Double replacement reaction
Correct answer: C
Rationale: The given chemical equation represents a single replacement reaction. In this reaction, aluminum (Al) displaces hydrogen in sulfuric acid (H2SO4), forming aluminum sulfate (Al2(SO4)3) and releasing nitric acid (HNO3). Single replacement reactions involve an element replacing another element in a compound, which is evident in this reaction. Choice A, Decomposition reaction, is incorrect because decomposition reactions involve a single compound breaking down into two or more substances. Choice B, Synthesis reaction, is incorrect as it involves the combination of two or more substances to form a more complex compound. Choice D, Double replacement reaction, is also incorrect as it involves an exchange of ions between two compounds to form two new compounds.
4. When an acid is added to a base, water and a salt form. What kinds of bonds form in these two compounds?
- A. Liquid and metallic
- B. Polar and nonpolar covalent
- C. Polar covalent and ionic
- D. Ionic only
Correct answer: C
Rationale: In water, the bond formed between the oxygen atom and the hydrogen atoms is a polar covalent bond. The oxygen atom attracts the shared electrons more strongly, creating a partial negative charge on the oxygen and a partial positive charge on the hydrogen atoms. In the salt formed, the bond between the metal cation and the nonmetal anion is predominantly an ionic bond. The metal cation donates electrons to the nonmetal anion, resulting in the formation of oppositely charged ions that are held together by electrostatic attractions. Choices A and B are incorrect because water and salts do not form bonds that are liquid and metallic, or polar and nonpolar covalent. Choice D is incorrect as it oversimplifies the types of bonds present in water and salts, failing to differentiate between the covalent bond in water and the ionic bond in the salt.
5. How many electrons are shared in a single covalent bond?
- A. 1
- B. 2
- C. 3
- D. 4
Correct answer: B
Rationale: The correct answer is B: '2'. In a single covalent bond, two electrons are shared between two atoms. Each atom contributes one electron to form the bond, resulting in the sharing of a total of two electrons. Choice A is incorrect because a single covalent bond involves the sharing of two electrons, not one. Choices C and D are incorrect as they do not represent the correct number of electrons shared in a single covalent bond.
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