Chemistry HESI A2 Quizlet

Correct Answer: C

Rationale: The correct answer is C: Atomic number. The atomic number represents the number of protons an element has in its nucleus. This is a fundamental property of an element and determines its identity on the periodic table. Atomic mass (A) is the total combined mass of protons and neutrons in an atom. Mass number (B) is the sum of protons and neutrons in the nucleus. Neutron number (D) is the number of neutrons in an atom, which can vary for isotopes of the same element. Therefore, the atomic number is the specific number of protons in an element, making it the correct choice.

Correct Answer: C

Rationale: Alpha particles are positively charged and relatively large, so they have low penetrating power. A piece of paper can stop alpha particles because the paper's thickness provides enough material for the particles to collide with and lose their energy through ionization. Aluminum foil and glass are not thick enough to effectively stop alpha particles. Plastic, depending on its thickness, may not provide sufficient shielding to stop alpha particles completely. In summary, the correct answer is C because the thickness of a piece of paper is sufficient to stop alpha particles, while the other choices are not adequate for effective shielding.

Correct Answer: C

Rationale: The correct answer is C: Hydrogen bonding. Hydrogen bonding is the strongest intermolecular force due to the high electronegativity difference between hydrogen and elements like nitrogen, oxygen, or fluorine, leading to a strong partial positive charge on hydrogen. This allows for a strong attraction with the partial negative charge on the electronegative atom of another molecule. Dipole interactions (A) are weaker than hydrogen bonding, dispersion forces (B) are the weakest intermolecular force, and Van der Waals forces (D) are a broad term that encompasses all intermolecular forces, including hydrogen bonding.

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 because a balanced chemical equation must satisfy the law of conservation of mass. This means that the number of atoms of each element must be the same on both the reactant and product sides. This ensures that no atoms are gained or lost during a chemical reaction. Explanation for why the other choices are incorrect: B: An equation with more products than reactants does not follow the law of conservation of mass. C: Balancing the number of molecules is important, but the key factor is balancing the number of atoms of each element. D: Equal masses on both sides do not necessarily guarantee that the number of atoms of each element is the same.