HESI A2
HESI A2 Chemistry Practice Test
1. Which scientific principle predicts that the solubility of a gas or volatile substance in a liquid is proportional to the partial pressure of the substance over the liquid (P = kC)?
- A. Boyle's Law
- B. Gay-Lussac's Law
- C. Henry's Law
- D. Charles' Law
Correct answer: C
Rationale: Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. The equation P = kC represents Henry's Law, where P is the partial pressure of the gas, C is the concentration of the gas in the liquid, and k is a constant. This law is applicable to dilute solutions where the gas does not significantly affect the liquid's volume. Therefore, in the context of gas solubility in liquids, Henry's Law is the appropriate principle that describes the relationship between solubility and partial pressure. Boyle's Law relates the pressure and volume of a gas at constant temperature, Gay-Lussac's Law deals with the pressure and temperature relationship of a gas at constant volume, and Charles' Law describes the relationship between the volume and temperature of a gas at constant pressure. These laws are not directly related to the solubility of gases in liquids, making them incorrect choices for this question.
2. When elements with low electronegativity (almost empty outer shells) react with elements with high electronegativity (mostly full outer shells), they tend to transfer electrons from the low electronegative element to the high electronegative element. This transfer results in the formation of what type of bonds?
- A. Hydrogen
- B. Covalent
- C. Ionic
- D. Nuclear
Correct answer: C
Rationale: The correct answer is C: Ionic. When elements with low electronegativity (almost empty outer shells) react with elements with high electronegativity (mostly full outer shells), they tend to transfer electrons from the low electronegative element to the high electronegative element. This transfer results in the formation of ionic bonds, where one element becomes positively charged (cation) and the other element becomes negatively charged (anion). Ionic bonds are formed through the attraction between these opposite charges, leading to a strong bond between the two elements. Choice A, Hydrogen, is incorrect because hydrogen is not involved in the described electron transfer process to form ionic bonds. Choice B, Covalent, is incorrect because covalent bonds involve the sharing of electrons between atoms, not the transfer of electrons as seen in the formation of ionic bonds. Choice D, Nuclear, is incorrect as nuclear bonds are not a recognized type of chemical bond. Therefore, the most appropriate answer is C: Ionic bonds.
3. Which of the following lists four factors that affect rates of reaction?
- A. Barometric pressure, particle size, concentration, and the presence of a facilitator
- B. Temperature, particle size, concentration, and the presence of a catalyst
- C. Temperature, container material, elevation, and the presence of instability
- D. Volatility, particle size, concentration, and the presence of a catalyst
Correct answer: B
Rationale: The correct answer is B. The factors that influence rates of reaction are temperature, particle size, concentration, and the presence of a catalyst. Temperature affects the speed of molecules, particle size impacts the available surface area for reactions, concentration influences the collision frequency between reactant molecules, and catalysts accelerate reactions by providing an alternative pathway with lower activation energy. Choices A, C, and D are incorrect as they either include irrelevant factors that do not affect reaction rates (barometric pressure, container material, elevation, and volatility) or lack important factors that do influence reaction rates (like a catalyst).
4. Which, if any, of the following statements is false?
- A. In an endothermic process, solubility typically decreases with an increase in temperature and increases if the temperature decreases
- B. In an exothermic process, solubility decreases with an increase in temperature
- C. All of the Above
- D. None of the Above
Correct answer: A
Rationale: Statement A is false. In an endothermic process, solubility typically decreases with an increase in temperature and increases if the temperature decreases. When heat is added to an endothermic process, it disrupts the intermolecular forces holding the solute particles together, making them more likely to dissolve. Therefore, higher temperatures generally lead to increased solubility in an endothermic process. Statement B is correct as in an exothermic process, solubility usually decreases with an increase in temperature due to the excess heat causing solute particles to come out of solution. As Statements A and B are contradictory, the answer cannot be 'All of the Above' or 'None of the Above.'
5. What is the spontaneous, random movement of small particles suspended in a liquid, caused by the unbalanced impacts of molecules on the particle?
- A. Brownian motion
- B. Grey's kinesis
- C. Boyle's wave
- D. None of the above
Correct answer: A
Rationale: Brownian motion is the correct choice as it specifically refers to the spontaneous, random movement of small particles suspended in a liquid, caused by the unbalanced impacts of molecules on the particle. This phenomenon was observed and documented by Robert Brown, leading to the discovery of the existence of molecules. Grey's kinesis and Boyle's wave are not scientifically recognized terms related to this concept.
Similar Questions
Access More Features
HESI A2 Basic
$49/ 30 days
- 3,000 Questions with answers
- 30 days access @ $49
HESI A2 Premium
$99/ 90 days
- Actual HESI A 2 Questions
- 3,000 questions with answers
- 90 days access @ $99