HESI A2 Chemistry Questions

Correct Answer: A

Rationale: The correct answer is A: Neutralization reaction. In this reaction, an acid and a base combine to form water and a salt. This process involves the transfer of protons from the acid to the base, resulting in the formation of water and a salt. Neutralization reactions are characterized by the formation of a neutral product (water) from the acidic and basic reactants. Option B: Decomposition reaction involves a compound breaking down into simpler substances. Option C: Combustion reaction involves a substance reacting with oxygen to produce heat and light. Option D: Redox reaction involves the transfer of electrons between reactants. These options do not accurately describe the reaction between an acid and a base to form water and salt.

Correct Answer: A

Rationale: The correct answer is A: A reaction that absorbs heat. Endothermic reactions absorb heat from their surroundings, causing a decrease in temperature. This is due to the breaking of chemical bonds which requires energy input. Choice B is incorrect as exothermic reactions release heat. Choice C is incorrect as all reactions involve heat to some extent. Choice D is incorrect as endothermic reactions result in a decrease in temperature due to heat absorption.

Correct Answer: C

Rationale: The correct answer is C: Evaporation. During evaporation, a liquid changes into a gas at the surface level due to the absorption of heat energy. This process occurs at temperatures below the boiling point of the liquid. Condensation (Choice A) is the opposite process, where a gas turns into a liquid. Sublimation (Choice B) is the phase change from solid directly to gas without passing through the liquid phase. Melting (Choice D) is the phase change from solid to liquid. Therefore, the correct choice for the phase change from liquid to gas is evaporation.

Correct Answer: A

Rationale: The correct answer is A: Covalent bond. In a covalent bond, two atoms share electrons to complete their outer electron shells and achieve stability. This sharing results in a strong bond between the atoms. Ionic bonds involve the transfer of electrons, metallic bonds involve a "sea" of shared electrons in a metal lattice, and hydrogen bonds are weaker interactions between a hydrogen atom and an electronegative atom. Covalent bonds are the only option where electrons are shared between atoms to form a stable bond.

Correct Answer: A

Rationale: The correct answer is A: Neutralization reaction. In this reaction, an acid and a base combine to form water and a salt. This process involves the transfer of protons from the acid to the base, resulting in the formation of water and a salt. Neutralization reactions are characterized by the formation of a neutral product (water) from the acidic and basic reactants. Option B: Decomposition reaction involves a compound breaking down into simpler substances. Option C: Combustion reaction involves a substance reacting with oxygen to produce heat and light. Option D: Redox reaction involves the transfer of electrons between reactants. These options do not accurately describe the reaction between an acid and a base to form water and salt.