HESI A2
HESI A2 Chemistry Practice Questions
1. Which of the following represents a hydride ion?
- A. Hâ»
- B. Hâº
- C. OHâ»
- D. HCl
Correct answer: A
Rationale: The hydride ion is denoted by Hâ», indicating that it has gained an extra electron to complete its valence shell, resulting in a full octet and a net charge of -1. This ion is commonly found in metal hydrides and plays a significant role in various chemical reactions. Option B, Hâº, represents a proton with a positive charge. Option C, OHâ», represents the hydroxide ion, consisting of oxygen and hydrogen. Option D, HCl, is a compound composed of hydrogen and chlorine ions, not a hydride ion.
2. What is the normal body temperature in °C?
- A. 36°C
- B. 37°C
- C. 35°C
- D. 40°C
Correct answer: B
Rationale: The normal body temperature for humans is 37°C. This temperature is considered average and is a standard reference point for assessing an individual's health status. It is essential for the body to maintain this temperature to ensure optimal functioning of various physiological processes. Choice A (36°C) is incorrect as it is slightly below the normal body temperature. Choice C (35°C) is also incorrect as it is significantly lower than the normal body temperature. Choice D (40°C) is incorrect as it is significantly higher than the normal body temperature and would indicate a fever or other health issue.
3. Which statement is true of a saturated solution?
- A. It has more solute than can dissolve in the solvent.
- B. It has less solute that can dissolve in the solvent.
- C. It has the maximum concentration of the solute dissolved in the solvent.
- D. It contains a precipitate that lowers the concentration of the solute in the solvent.
Correct answer: C
Rationale: A saturated solution contains the maximum concentration of solute that can be dissolved in a specific amount of solvent at a particular temperature. Once a solution is saturated, adding more solute will not increase its concentration since the excess solute will not dissolve and will instead form a precipitate, indicating that the solution is at its maximum capacity. Choices A, B, and D are incorrect because a saturated solution has reached its limit in dissolving solute, so it cannot contain more solute than it can dissolve (choice A), less solute than it can dissolve (choice B), or a precipitate that lowers the concentration of the solute in the solvent (choice D).
4. What is the correct name of AgNO₃?
- A. Argent nitrous
- B. Argent oxide
- C. Silver nitrite
- D. Silver nitrate
Correct answer: D
Rationale: The correct name for AgNO₃ is silver nitrate. In chemical nomenclature, the element symbol Ag represents silver, and the polyatomic ion NO₃ is known as nitrate. Therefore, when the silver ion (Agâº) combines with the nitrate ion (NO₃â»), the resulting compound is named silver nitrate (AgNO₃). Choices A, B, and C are incorrect because they do not accurately represent the composition of AgNO₃. Argent nitrous (Choice A) and Argent oxide (Choice B) do not reflect the correct anion, and Silver nitrite (Choice C) uses a different anion altogether.
5. What type of bond is an electrostatic attraction between two oppositely charged ions?
- A. Covalent
- B. Metallic
- C. Ionic
- D. Hydrogen
Correct answer: C
Rationale: An ionic bond forms when one atom transfers electrons to another, resulting in the formation of positively and negatively charged ions. The attraction between these oppositely charged ions creates an electrostatic bond, known as an ionic bond. Choice A, covalent bonds, involve the sharing of electrons, not the transfer. Choice B, metallic bonds, occur between metal atoms and involve a 'sea of electrons' that are delocalized. Choice D, hydrogen bonds, are much weaker interactions between hydrogen atoms and other electronegative atoms like oxygen or nitrogen.
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