HESI A2
Chemistry HESI A2 Quizlet
1. What is the process of breaking bonds and forming new bonds to create new chemical compounds?
- A. Physical reaction
- B. Chemical reaction
- C. Nuclear reaction
- D. Mechanical reaction
Correct answer: B
Rationale: A chemical reaction involves the breaking and forming of bonds to create new substances. During a chemical reaction, the original chemical bonds are broken, and new bonds are formed to produce one or more new substances with different properties from the reactants. This transformation is a fundamental concept in chemistry and distinguishes chemical reactions from physical, nuclear, or mechanical reactions. Choice A, 'Physical reaction,' does not involve the breaking and forming of chemical bonds but rather changes in physical state or appearance. Choice C, 'Nuclear reaction,' involves changes in the nuclei of atoms, not the breaking and forming of chemical bonds. Choice D, 'Mechanical reaction,' refers to reactions involving physical forces or movements, not the breaking and forming of chemical bonds as in a chemical reaction.
2. What are the three types of radiation?
- A. Alpha, beta, gamma
- B. Alpha, beta, delta
- C. Gamma, delta, epsilon
- D. Beta, gamma, epsilon
Correct answer: A
Rationale: The correct answer is Alpha, beta, gamma. Alpha radiation consists of helium nuclei, beta radiation comprises electrons or positrons, and gamma radiation is high-energy electromagnetic radiation. Choice B, delta, is incorrect as delta is not a type of radiation. Choice C, gamma, delta, epsilon, and Choice D, beta, gamma, epsilon, are incorrect as they do not include the three standard types of radiation.
3. What is the correct formula for potassium chloride?
- A. NaCl
- B. KCl
- C. KCl
- D. ClK
Correct answer: B
Rationale: The correct formula for potassium chloride is KCl. In chemical formulas, the symbol for the cation (positive ion) comes first followed by the symbol for the anion (negative ion). Potassium is represented by the symbol K, while chloride is represented by the symbol Cl. Therefore, the formula for potassium chloride is KCl. Choice A (NaCl) is the formula for sodium chloride, not potassium chloride. Choice C is a duplicate of choice B, and choice D (ClK) is an incorrect arrangement of the symbols for potassium and chloride.
4. On the periodic table, where are atoms with the largest atomic radius located?
- A. At the top of their group
- B. In the middle of their group
- C. At the bottom of their group
- D. Along the right-hand side
Correct answer: C
Rationale: Atoms with the largest atomic radius are located at the bottom of their group on the periodic table. This is because atomic radius increases down a group due to the addition of more energy levels or shells of electrons. As you move down a group, the outermost electrons are further away from the nucleus, leading to an increase in atomic radius. Choice A 'At the top of their group' is incorrect because atomic radius decreases going up within a group. Choice B 'In the middle of their group' is incorrect as the atomic radius generally increases as you go down a group, not in the middle. Choice D 'Along the right-hand side' is incorrect because atomic radius tends to decrease from left to right across a period on the periodic table due to increased nuclear charge and effective nuclear charge.
5. Which of these intermolecular forces would result in the lowest boiling point?
- A. Dipole-dipole interaction
- B. London dispersion force
- C. Keesom interaction
- D. Hydrogen bonding
Correct answer: B
Rationale: The London dispersion force is the weakest intermolecular force among the options provided. These forces are present in all molecules and are caused by temporary fluctuations in electron density, resulting in temporary dipoles. Since London dispersion forces are generally weaker than dipole-dipole interactions, Keesom interactions, and hydrogen bonding, a substance with London dispersion forces as the primary intermolecular force would have the lowest boiling point due to the weaker intermolecular forces holding the molecules together. Dipole-dipole interactions, Keesom interactions, and hydrogen bonding are stronger intermolecular forces compared to London dispersion forces, resulting in higher boiling points for substances that exhibit these interactions.
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