Chemistry HESI A2 Practice Test

Correct Answer: B

Rationale: The correct formula for silver hydroxide is AgOH. Silver is a transition metal with a +1 charge, and hydroxide is OH⁻. To balance the charges, one silver ion combines with one hydroxide ion to form AgOH. Choice A (AgO) is incorrect because it does not include the hydroxide ion. Choice C (AgH) is incorrect as it suggests silver bonding with hydrogen, which is not the case. Choice D (AgH₂O) is incorrect as it implies silver bonding with water molecules, which is not the formula for silver hydroxide.

Correct Answer: B

Rationale: The correct answer is B: Absolute zero. Kelvin is based on the concept of absolute zero, which is the coldest possible temperature where particles have minimal kinetic energy. This forms the foundation for the Kelvin temperature scale. A: Freezing point is incorrect because Kelvin is not specifically based on the freezing point of any substance. C: Boiling point is incorrect as Kelvin is not directly linked to the boiling point of any substance. D: Evaporation point is incorrect because Kelvin does not relate to the point at which a substance undergoes evaporation.

Correct Answer: D

Rationale: The correct answer is D: Crystalline shape. Ionic compounds have a regular, repeating arrangement of ions in a crystal lattice structure due to strong electrostatic forces between oppositely charged ions. This leads to the formation of distinct geometric shapes, known as crystalline shapes. Choice A is incorrect because ionic compounds typically have high melting points due to strong ionic bonds. Choice B is incorrect as ionic compounds are good conductors when dissolved in water or in a molten state. Choice C is incorrect because ionic compounds involve transfer, not sharing, of electrons between ions.

Correct Answer: D

Rationale: The correct answer is D: OH⁻. In water solutions of bases, OH⁻ ions are dominant as they are responsible for the basic properties. Bases release OH⁻ ions when dissolved in water, leading to an increase in pH. MgCl₂ and 2HCl do not contribute to basicity as they do not release OH⁻ ions. H⁺ ions, found in strong acids, are associated with acidic properties and would not dominate in a base solution.

Correct Answer: C

Rationale: The given chemical equation shows aluminum replacing hydrogen in sulfuric acid, which is a single replacement reaction. In this type of reaction, one element displaces another in a compound. Here, Al replaces H in H2SO4 to form Al2(SO4)3 and HNO3. The other choices are incorrect because a decomposition reaction involves a single compound breaking down into simpler substances, a synthesis reaction involves two or more substances combining to form a new compound, and a double replacement reaction involves the exchange of ions between two compounds.