Chemistry HESI A2 Quizlet

Correct Answer: B

Rationale: The correct answer is B (2). In a double covalent bond, two electron pairs are shared between two atoms. This is achieved by the sharing of two pairs of electrons, resulting in a total of four electrons being shared. However, since each pair consists of two electrons, the number of electron pairs shared to form a double covalent bond is 2. Choices A, C, and D are incorrect because a double bond involves the sharing of 2 electron pairs, not 1, 3, or 4 pairs.

Correct Answer: A

Rationale: The correct answer is A: Decomposition. This reaction involves breaking down a compound into simpler components through the use of heat, light, or electricity. Decomposition reactions are the opposite of synthesis reactions, where compounds are formed from simpler substances. Combustion involves the reaction of a substance with oxygen to produce heat and light. Single replacement reactions occur when one element replaces another in a compound. In this context, only decomposition aligns with the process of breaking down a compound into its component parts.

Correct Answer: C

Rationale: The correct answer is C: Combustion. Combustion is a chemical reaction where a compound reacts with oxygen to produce heat, light, and often carbon dioxide and water. In this type of reaction, oxygen is a reactant and typically a hydrocarbon or organic compound is the fuel. Decomposition involves a compound breaking down into simpler substances, synthesis is when two or more substances combine to form a more complex compound, and single replacement is when one element replaces another in a compound. Combustion specifically involves the reaction with oxygen, making it the correct choice in this scenario.

Correct Answer: C

Rationale: Increasing the surface area of a reactant increases the number of exposed particles available for collision, leading to more frequent and successful collisions. This results in an increased reaction rate. Choice A is incorrect because more surface area facilitates faster reactions. Choice B is incorrect as surface area affects reaction rate. Choice D is incorrect as increasing surface area does not stop the reaction; it actually accelerates it.

Correct Answer: D

Rationale: The correct answer is D: Molar mass. One mole of a substance represents the molar mass, which is the mass of one mole of that substance in grams. This is calculated by summing the atomic masses of all the atoms in the chemical formula. The molar mass is expressed in g/mol and is a fundamental concept in chemistry for performing various calculations. A: Atomic mass refers to the mass of an individual atom of an element, not one mole of a substance. B: Mass number refers to the total number of protons and neutrons in an atom's nucleus, not the mass of one mole of a substance. C: Molecular weight is the sum of the atomic weights of the atoms in a molecule, not the mass of one mole of a substance.