Chemistry HESI A2 Practice Test

Correct Answer: B

Rationale: The molar mass of a substance is the mass of one mole of that substance. The molar mass of water (H2O) can be calculated by adding the atomic masses of its components (2 hydrogen atoms + 1 oxygen atom). Hydrogen's atomic mass is approximately 1 g/mol, and oxygen's atomic mass is approximately 16 g/mol. Therefore, the molar mass of water is 2(1) + 16 = 18 g/mol. This makes choice B (18 g/mol) the correct answer. Choices A, C, and D are incorrect because they do not reflect the accurate molar mass calculation of water based on the atomic masses of its components.

Correct Answer: B

Rationale: The correct answer is B: Anion. When an atom gains one or more electrons, it becomes negatively charged, forming an anion. This process is known as gaining electron(s) to achieve a stable electron configuration. A cation (A) is formed when an atom loses electron(s) and becomes positively charged. Isotope (C) refers to atoms of the same element with different numbers of neutrons. Electron (D) is a fundamental subatomic particle, not a term for an atom gaining electrons.

Correct Answer: D

Rationale: Step 1: Define hydrogen bonding as a special type of dipole-dipole interaction. Step 2: Highlight that hydrogen bonding occurs between a hydrogen atom and highly electronegative atom (N, O, or F). Step 3: Emphasize that hydrogen bonding is stronger due to the large electronegativity difference between hydrogen and the other atom. Step 4: Compare the strength of hydrogen bonding to the other types of intermolecular forces. Step 5: Conclude that hydrogen bonding is the strongest intermolecular force due to its specific characteristics and stronger attraction compared to dipole-dipole interaction, London dispersion force, and Keesom interaction.

Correct Answer: C

Rationale: To calculate molarity, we need to find the number of moles of solute (glucose) and the volume of the solution. 1. Calculate moles of glucose: 5g / 180 g/mol = 0.0278 mol 2. Calculate total mass of the solution: 5g (glucose) + 100g (water) = 105g 3. Calculate molarity: 0.0278 mol / 0.105 kg = 0.2667 M ≈ 2.8M (Choice C) Rationale: Molarity is moles of solute per liter of solution. The correct answer is C because it correctly calculates the molarity of the solution. Other choices are incorrect as they do not provide the accurate molarity value based on the given information.

Correct Answer: B

Rationale: Failed to generate a rationale after 5 retries.