HESI A2 Chemistry Questions

Correct Answer: A

Rationale: The correct answer is A: Decomposition reaction. In a decomposition reaction, a compound is broken down into its individual components. This process involves the breaking of chemical bonds within the compound, resulting in the formation of simpler substances. This type of reaction is characterized by one reactant and multiple products. In contrast, the other choices - B: Combustion reaction, C: Neutralization reaction, and D: Single displacement reaction - do not involve the breaking down of a compound into its components but rather involve different types of chemical transformations. Combustion reaction involves the reaction of a substance with oxygen to produce heat and light, neutralization reaction involves the reaction between an acid and a base to form water and a salt, and single displacement reaction involves the replacement of one element in a compound by another element.

Correct Answer: C

Rationale: The correct answer is C: Ammonia. Ammonia is a base because it can accept protons (H+ ions) to form ammonium ions (NH4+). It can also react with water to form ammonium hydroxide, which is a strong base. Water (choice A) is neutral, not a base. Sodium chloride (choice B) is a salt formed from the reaction of a strong acid and a strong base, not a base itself. "Salt" (choice D) is a general term for any ionic compound formed from the neutralization of an acid and a base, not specifically a base.

Correct Answer: B

Rationale: The correct answer is B: Fluorine. Fluorine is the most electronegative element because it has the highest electronegativity value on the periodic table. Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. Fluorine has the highest electronegativity value of 3.98, indicating its strong ability to attract electrons. Oxygen (A) is also highly electronegative but has a lower value than fluorine. Nitrogen (C) is less electronegative than oxygen. Sodium (D) is a metal and has low electronegativity compared to the nonmetals listed.

Correct Answer: A

Rationale: The correct answer is A: Fluorine. Fluorine has the highest electronegativity because it has the smallest atomic size among the choices, leading to a stronger attraction for electrons. This makes it more likely to attract electrons in a chemical bond. Chlorine, Nitrogen, and Oxygen have lower electronegativities compared to Fluorine due to their larger atomic sizes, resulting in weaker electron-attracting capabilities. Remember, electronegativity generally increases across a period from left to right in the periodic table.

Correct Answer: B

Rationale: The correct answer is B: Liquid. Liquids have a definite volume, meaning they have a fixed amount of space they occupy, but they take the shape of their container because their particles are not arranged in a fixed pattern like solids. In contrast, gases (choice A) have neither a definite volume nor a definite shape, as their particles are free to move and fill the entire space of their container. Solids (choice C) have both a definite volume and shape due to their tightly packed and ordered particles. Plasma (choice D) is a state of matter where particles are highly energized and ionized, lacking a definite shape or volume.