HESI A2
HESI A2 Chemistry Practice Questions
1. What is the correct electron configuration for nitrogen?
- A. 1s² 2s²
- B. 1s² 2s² 2p²
- C. 1s² 2s² 2p³
- D. 1s² 2s² 2p⁴
Correct answer: C
Rationale: The electron configuration of nitrogen is determined by its atomic number, which is 7. Nitrogen has 7 electrons. Following the order of filling orbitals, the electron configuration for nitrogen is 1s² 2s² 2p³. This means the first energy level is filled with 2 electrons in the 1s orbital, the second energy level is filled with 2 electrons in the 2s orbital, and 3 electrons in the 2p orbital. Each orbital can hold a specific number of electrons, and nitrogen, with its 7 electrons, fits this configuration. Choice A is incorrect because it does not account for all the electrons in the nitrogen atom. Choice B is incorrect as it only represents 6 electrons, not the 7 electrons in nitrogen. Choice D is incorrect as it represents 8 electrons, which is not the correct electron configuration for nitrogen.
2. Which element has the highest electronegativity?
- A. Fluorine
- B. Chlorine
- C. Nitrogen
- D. Oxygen
Correct answer: A
Rationale: Fluorine has the highest electronegativity among the elements listed. Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. Fluorine, being the most electronegative element on the periodic table, has the strongest ability to attract electrons towards itself compared to chlorine, nitrogen, and oxygen. Therefore, fluorine is the correct answer. Chlorine, nitrogen, and oxygen have lower electronegativities compared to fluorine, making them incorrect choices for the element with the highest electronegativity.
3. Which material has the smallest specific heat capacity?
- A. water
- B. wood
- C. aluminum
- D. glass
Correct answer: C
Rationale: Specific heat capacity is the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. Among the options provided, aluminum has the smallest specific heat capacity. This means that it requires the least amount of heat to raise its temperature compared to water, wood, and glass. Water has a high specific heat capacity, making it resistant to temperature changes, while wood and glass have higher specific heat capacities compared to aluminum.
4. To the nearest whole number, what is the mass of one mole of sodium chloride?
- A. 36 g/mol
- B. 43 g/mol
- C. 58 g/mol
- D. 72 g/mol
Correct answer: C
Rationale: The molar mass of sodium chloride (NaCl) is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl). The atomic mass of sodium is approximately 23 g/mol and chlorine is approximately 35.5 g/mol. Adding these two atomic masses gives us a molar mass of approximately 58 g/mol for sodium chloride (NaCl). Therefore, the correct answer is C, 58 g/mol. Choice A (36 g/mol) is incorrect as it does not account for the individual atomic masses of sodium and chlorine. Choice B (43 g/mol) and choice D (72 g/mol) are also incorrect as they do not reflect the accurate molar mass of sodium chloride.
5. What are the three types of radiation?
- A. Alpha, beta, gamma
- B. Alpha, beta, delta
- C. Gamma, delta, epsilon
- D. Beta, gamma, epsilon
Correct answer: A
Rationale: The correct answer is Alpha, beta, gamma. Alpha radiation consists of helium nuclei, beta radiation comprises electrons or positrons, and gamma radiation is high-energy electromagnetic radiation. Choice B, delta, is incorrect as delta is not a type of radiation. Choice C, gamma, delta, epsilon, and Choice D, beta, gamma, epsilon, are incorrect as they do not include the three standard types of radiation.
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