Chemistry HESI A2 Quizlet

Correct Answer: A

Rationale: The correct answer is A: Hydrogen and oxygen. Water decomposes into hydrogen and oxygen through a process called electrolysis. In this process, an electric current is passed through water, causing it to break down into its constituent elements. Hydrogen is produced at the cathode, while oxygen is produced at the anode. This is a well-known and scientifically proven reaction. Choices B, C, and D are incorrect because water does not decompose into carbon dioxide, nitrogen, or methane under normal conditions. This can be confirmed by studying the chemical properties and reactions of water.

Correct Answer: A

Rationale: To increase the reaction rate of a chemical reaction, increasing the temperature is the correct answer. This is because raising the temperature provides reactant molecules with more kinetic energy, leading to more frequent and energetic collisions, which increases the likelihood of successful collisions and hence the reaction rate. Increasing the surface area (choice B) can enhance the reaction rate for solid reactants but is not universally applicable. Increasing the concentration of reactants (choice C) can increase the reaction rate by providing more reactant molecules for collisions, but it may not always be the most effective method compared to temperature. Adding a catalyst (choice D) can lower the activation energy and speed up the reaction rate, but it is not the only way to increase reaction rates.

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: A

Rationale: The correct answer is A: 1. In a single bond, only one pair of electrons is shared between two atoms, resulting in a stable bond. This shared pair of electrons creates a strong attraction between the atoms, holding them together. The other choices (B, C, D) are incorrect as they represent the number of pairs of electrons shared in double, triple, or quadruple bonds, respectively, which involve 2, 3, or 4 pairs of electrons being shared, not in a single bond. Thus, the correct answer is A because a single bond involves only one pair of shared electrons.

Correct Answer: C

Rationale: The correct answer is C: Atomic mass. Atomic mass refers to the average mass of an element's isotopes as they occur in nature. This is calculated by taking into account the abundance of each isotope. The atomic number (A) is the number of protons in an atom's nucleus, not the average mass. The mass number (B) is the sum of protons and neutrons in an atom's nucleus, not the average mass. Neutron number (D) is simply the number of neutrons in an atom's nucleus, not the average mass. Therefore, the correct term for the average mass of isotopes is atomic mass.