the breaking of bonds and reforming of new bonds to create new chemical compounds

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. Cobalt-60 has a half-life of 5 years. If you start with 20 g of cobalt-60, how much is left after 10 years?

A. 15 g
B. 10 g
C. 5 g
D. 2.5 g

Correct answer: C

Rationale: Cobalt-60's half-life of 5 years means that after 5 years, half of the initial amount remains. Therefore, after 10 years, a quarter (half of a half) of the initial amount will remain. Starting with 20 g, after 10 years, 5 g of cobalt-60 will be left. Choice A (15 g) is incorrect because it assumes a linear decrease, not considering the exponential decay characteristic of radioactive substances. Choice B (10 g) is incorrect as it overlooks that after 10 years, more decay has occurred. Choice D (2.5 g) is incorrect as it represents only an eighth of the initial amount after 10 years, not a quarter.

3. What is the pH of acids?

A. 7.5
B. < 7
C. > 7
D. 7

Correct answer: B

Rationale: The correct answer is B: < 7. Acids have a pH lower than 7, indicating higher acidity. A pH below 7 signifies an acidic solution, with lower values indicating stronger acids. Choice A (7.5) is incorrect as it is greater than 7, which is alkaline. Choice C (> 7) is incorrect as values greater than 7 represent alkaline/basic solutions. Choice D (7) is incorrect because a pH of 7 is neutral, not acidic.

4. In what type of covalent compounds are dispersion forces typically found?

A. Polar
B. Non-polar
C. Ionic
D. Hydrogen

Correct answer: B

Rationale: Dispersion forces, also known as London dispersion forces, are the weakest intermolecular forces that occur in non-polar covalent compounds. These forces result from temporary shifts in electron density within molecules, creating temporary dipoles. As a result, non-polar molecules, which lack a permanent dipole moment, can experience these dispersion forces. Polar compounds exhibit stronger intermolecular forces such as dipole-dipole interactions or hydrogen bonding, while ionic compounds involve electrostatic interactions between ions. Therefore, the correct answer is non-polar (choice B). Choices A, C, and D are incorrect because dispersion forces are typically found in non-polar covalent compounds, not polar, ionic, or hydrogen-bonded compounds.

5. Which chemical reaction involves the formation of a single product from two or more reactants?

A. Synthesis reaction
B. Combustion reaction
C. Decomposition reaction
D. Double displacement reaction

Correct answer: A

Rationale: A synthesis reaction involves the combination of two or more reactants to form a single product. This type of reaction is characterized by the merging of substances to create a more complex compound. In a synthesis reaction, the reactants bond together to form a new product, making it the correct choice for this scenario. Combustion reactions involve the rapid combination of oxygen with another substance, resulting in the release of energy in the form of heat and light. Decomposition reactions entail the breakdown of a compound into simpler substances, often through the application of heat or electricity. Double displacement reactions involve the exchange of ions between two compounds, leading to the formation of two new compounds.