HESI A2 Chemistry Practice Questions - Nurselytic

Correct Answer: D

Rationale: The correct answer is D, lye. Lye, also known as sodium hydroxide (NaOH), is a strong base that forms hydroxide ions (OH-) when placed in water. When lye dissolves in water, it dissociates into sodium ions (Na+) and hydroxide ions, making it an alkaline substance. Lemon juice, battery acid, and vinegar do not form hydroxide ions when placed in water. Lemon juice contains citric acid, battery acid contains sulfuric acid, and vinegar contains acetic acid, none of which produce hydroxide ions when dissolved in water.

Correct Answer: B

Rationale: The correct answer is B, Pyridine (C5H5N). Pyridine is not a hydrocarbon because it contains nitrogen (N) in its molecular structure, in addition to carbon (
C) and hydrogen (H) atoms. Hydrocarbons consist solely of carbon and hydrogen atoms. Methane (CH4), ethane (C2H6), and propane (C3H8) are all examples of hydrocarbons as they only contain carbon and hydrogen atoms, making them organic compounds known for their combustion properties.

Correct Answer: A

Rationale: The correct answer is A. When a substance is heated, the kinetic energy of particles increases, causing them to move faster. This increased movement allows the particles to spread out more rapidly, leading to a higher diffusion rate.
Choice B is incorrect because heating does not directly affect the space between particles.
Choice C is incorrect because heating does not necessarily lead to a decrease in the density of particles.
Choice D is incorrect because the size of particles does not necessarily increase when a substance is heated.
Therefore, the correct explanation for the increase in diffusion rate is the rise in kinetic energy of particles.

Correct Answer: C

Rationale: The correct formula for iron III oxide is Fe2O3. In this formula, Fe represents iron and O represents oxygen. Iron III oxide consists of two iron (Fe) ions combined with three oxygen (O) ions. Thus, the correct formula is Fe2O3.
Choice A (IO) is incorrect as it does not represent the correct combination of iron and oxygen ions.
Choice B (FeS) is incorrect as it represents iron sulfide, not iron III oxide.
Choice D (OFe₂₃) is incorrect as it does not follow the correct chemical nomenclature for iron III oxide.

Correct Answer: A

Rationale: Allotropes are different forms of the same element that exist in the same physical state but have different structures. The arrangement of atoms is what distinguishes one allotrope from another, determining their unique properties and characteristics. Gram atomic mass (
Choice
B) is a constant value for a specific element and does not change between different allotropes. Physical state (
Choice
C) refers to whether a substance is a solid, liquid, or gas, which can be the same for different allotropes of an element. Stability (
Choice
D) can vary between different allotropes, but it is not what always differentiates one allotrope from another.
Therefore, the correct answer is the arrangement of atoms, as it is the key factor that varies across different allotropes.