HESI A2
Chemistry HESI A2 Quizlet
1. What are the two types of chemical bonding?
- A. Covalent & hydrogen
- B. Ionic & covalent
- C. Ionic & hydrogen
- D. Covalent & metallic
Correct answer: B
Rationale: The correct answer is B: Ionic & covalent. Ionic bonding involves the transfer of electrons between atoms, resulting in the formation of positive and negative ions attracted to each other. Covalent bonding involves the sharing of electrons between atoms to achieve a stable electron configuration. Choice A is incorrect as hydrogen bonding is a type of intermolecular force, not a primary type of chemical bonding. Choice C is incorrect as hydrogen bonding is not a primary type of chemical bonding. Choice D is incorrect as metallic bonding involves the sharing of electrons in a 'sea of electrons' within a metal lattice, not covalent bonding.
2. What type of reaction occurs when an acid and a base react to form water and salt?
- A. Neutralization reaction
- B. Decomposition reaction
- C. Combustion reaction
- D. Redox reaction
Correct answer: A
Rationale: A neutralization reaction is the correct answer. In this type of reaction, an acid and a base combine to form water and salt. The acid donates a proton (H+) to the base, forming water, while the remaining ions combine to form a salt. This reaction results in the neutralization of both the acid and the base, hence the name 'neutralization reaction.' Choice B, decomposition reaction, is incorrect because it refers to a reaction where a compound breaks down into simpler substances. Choice C, combustion reaction, is incorrect as it involves a substance reacting with oxygen to produce heat and light. Choice D, redox reaction, is incorrect because it involves the transfer of electrons between reactants.
3. Which of the following represents a hydride ion?
- A. Hâ»
- B. Hâº
- C. OHâ»
- D. HCl
Correct answer: A
Rationale: The hydride ion is denoted by Hâ», indicating that it has gained an extra electron to complete its valence shell, resulting in a full octet and a net charge of -1. This ion is commonly found in metal hydrides and plays a significant role in various chemical reactions. Option B, Hâº, represents a proton with a positive charge. Option C, OHâ», represents the hydroxide ion, consisting of oxygen and hydrogen. Option D, HCl, is a compound composed of hydrogen and chlorine ions, not a hydride ion.
4. Which of these types of intermolecular force is the strongest?
- A. Dipole-dipole interaction
- B. London dispersion force
- C. Keesom interaction
- D. Hydrogen bonding
Correct answer: D
Rationale: Hydrogen bonding is the strongest type of intermolecular force among the options provided. It occurs when a hydrogen atom is covalently bonded to a highly electronegative atom (such as nitrogen, oxygen, or fluorine) and forms a strong electrostatic attraction with an unshared pair of electrons on another electronegative atom. This type of bond is stronger than dipole-dipole interactions, London dispersion forces, and Keesom interactions due to the significant electronegativity difference between the hydrogen and the electronegative atom involved in the bond. The presence of hydrogen bonding contributes to unique properties in substances, such as high boiling and melting points, making it a crucial force in various biological and chemical processes.
5. What is the typical oxidation state of oxygen in most compounds?
- A. -1
- B. -2
- C. 0
- D. -3
Correct answer: B
Rationale: The correct answer is B: "-2". Oxygen usually exhibits an oxidation state of -2 in most compounds. This is due to oxygen's high electronegativity, which causes it to attract electrons, leading to the gain of two electrons in chemical reactions. Choice A (-1) is incorrect because oxygen rarely has an oxidation state of -1 in compounds. Choice C (0) is incorrect as oxygen does not usually have an oxidation state of zero in compounds. Choice D (-3) is incorrect as oxygen does not commonly have an oxidation state of -3 in compounds.
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