HESI A2
HESI A2 Chemistry Questions
1. Which element has the highest atomic number?
- A. Uranium
- B. Hydrogen
- C. Radon
- D. Bismuth
Correct answer: A
Rationale: The correct answer is Uranium. The atomic number represents the number of protons in an atom's nucleus. Among the options provided, Uranium has the highest atomic number, which is 92. Hydrogen has an atomic number of 1, Radon has an atomic number of 86, and Bismuth has an atomic number of 83. Therefore, Uranium is the element with the highest atomic number in the given choices.
2. Which ion would you expect to dominate in water solutions of bases?
- A. MgCl₂
- B. 2HCl
- C. H⁺
- D. OH⁻
Correct answer: D
Rationale: In water solutions of bases, the dominant ion would be OH⁻ (hydroxide ion). Bases release OH⁻ ions when dissolved in water, increasing the concentration of hydroxide ions and leading to a higher pH. This is in contrast to acids, which release H⁺ ions. Therefore, in water solutions of bases, the presence of OH⁻ ions signifies the basic nature of the solution. Choices A, B, and C are incorrect because MgCl₂ is a salt, 2HCl is a compound consisting of two hydrogen ions and one chloride ion, and H⁺ represents a hydrogen ion typically associated with acids, not bases.
3. What is the name of the bond formed when two atoms share electrons?
- A. Covalent bond
- B. Ionic bond
- C. Metallic bond
- D. Hydrogen bond
Correct answer: A
Rationale: A covalent bond is formed when two atoms share electrons, creating a stable electron configuration. This sharing allows both atoms to achieve a full outer shell of electrons, leading to a stable molecule. In contrast, an ionic bond involves the transfer of electrons from one atom to another, resulting in the formation of ions with opposite charges. Metallic bonds are formed between metal atoms and involve a 'sea of electrons' that are delocalized and free to move. Hydrogen bonds are a type of intermolecular force, not a true chemical bond, and occur between a hydrogen atom and a highly electronegative atom like oxygen or nitrogen.
4. What is an alloy in which another metal is dissolved in mercury (Hg) called?
- A. Electrum
- B. Amalgam
- C. Solder
- D. Bronze
Correct answer: B
Rationale: An amalgam is a type of alloy where another metal is dissolved in mercury (Hg). This process forms a unique mixture that has various applications in dentistry, chemistry, and other fields. Electrum is a natural alloy of gold and silver, solder is a metal alloy used to join other metals together, and bronze is a copper-tin alloy. Therefore, the correct answer is B - Amalgam.
5. What is stoichiometry?
- A. The study of energy changes in chemical reactions
- B. The study of the mass relationships in chemical reactions
- C. The study of atomic structure
- D. The study of molecular geometry
Correct answer: B
Rationale: Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. It focuses on the calculation of the amounts of substances consumed and produced in a reaction based on the balanced chemical equation. Choice A is incorrect because the study of energy changes in chemical reactions falls under thermodynamics. Choice C is incorrect as atomic structure is related to the arrangement of atoms within molecules. Choice D is incorrect as molecular geometry deals with the spatial arrangement of atoms within molecules.
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