HESI A2
HESI A2 Chemistry Practice Questions
1. What is the net charge of an ionic compound?
- A. 0
- B. -1
- C. +1
- D. Variable
Correct answer: A
Rationale: The correct answer is A: 0. Ionic compounds have a net charge of 0 because they are formed by the combination of positively charged ions (cations) and negatively charged ions (anions) in a way that neutralizes their charges. This balanced combination results in an electrically neutral compound. Therefore, the net charge of an ionic compound is typically 0. Choices B, C, and D are incorrect because ionic compounds are designed to have a total neutral charge, with the positive charges balancing out the negative charges.
2. What is 0 K equal to in °C?
- A. -300°C
- B. -273°C
- C. -250°C
- D. -200°C
Correct answer: B
Rationale: 0 Kelvin, also known as absolute zero, is equal to -273°C. This is the point at which all molecular motion stops, making it the lowest possible temperature on the Kelvin scale. Choice A (-300°C) is incorrect as it is not the correct conversion of 0 K to °C. Choice C (-250°C) and Choice D (-200°C) are also incorrect as they do not correspond to the accurate conversion of 0 K to °C.
3. Which of these intermolecular forces might represent attraction between atoms of a noble gas?
- A. Dipole-dipole interaction
- B. London dispersion force
- C. Keesom interaction
- D. Hydrogen bonding
Correct answer: B
Rationale: Noble gases are non-polar molecules without a permanent dipole moment. The only intermolecular force applicable to noble gases is the London dispersion force, also known as Van der Waals forces. This force is a temporary attractive force resulting from the formation of temporary dipoles in non-polar molecules. Dipole-dipole interactions, Keesom interactions, and hydrogen bonding involve significant dipoles or hydrogen atoms bonded to electronegative atoms, which do not apply to noble gases.
4. What is the correct electron configuration for lithium?
- A. 1s²2s¹
- B. 1s²2s²
- C. 1s²2s¹2p¹
- D. 1s¹2s¹2p²
Correct answer: A
Rationale: The electron configuration for lithium is 1s²2s¹. Lithium has 3 electrons, and the configuration indicates that the first two electrons fill the 1s orbital, while the third electron fills the 2s orbital. Therefore, the correct electron configuration for lithium is 1s²2s¹. Choice B (1s²2s²) is incorrect as it represents the electron configuration for beryllium, not lithium. Choice C (1s²2s¹2p¹) includes the 2p orbital, which is not involved in lithium's electron configuration. Choice D (1s¹2s¹2p²) is incorrect as it does not accurately represent lithium's electron configuration.
5. What is the pH of a neutral solution?
- A. 7
- B. 0
- C. 14
- D. 4
Correct answer: A
Rationale: The correct answer is A: 7. A neutral solution has a pH of 7. In the pH scale, values below 7 are acidic, 7 is neutral, and values above 7 are basic. Therefore, a solution with a pH of 7 is considered neutral as it is neither acidic nor basic. Choices B, C, and D are incorrect because a pH of 0 indicates a strong acid, a pH of 14 indicates a strong base, and a pH of 4 indicates an acidic solution. None of these values represent a neutral solution.
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