Nursing Elites

1. What is the correct electron configuration for magnesium?

• A. 1s² 2s²
• B. 1s² 2s² 2p⁶
• C. 1s² 2s² 2p⁶ 3s²
• D. 1s² 2s² 2p⁶ 3s² 3p¹

Correct answer: C

Rationale: The electron configuration of an element is determined by following the Aufbau principle, which states that electrons fill orbitals starting from the lowest energy level. Magnesium has an atomic number of 12, meaning it has 12 electrons. The electron configuration of magnesium fills the 1s, 2s, 2p, and 3s orbitals to accommodate all 12 electrons. Therefore, the correct electron configuration for magnesium is 1s² 2s² 2p⁶ 3s². Choice A is incorrect as it only includes 4 electrons and stops at the 2s orbital. Choice B is incorrect as it includes 8 electrons and stops at the 2p orbital. Choice D is incorrect as it includes 13 electrons and extends to the 3p orbital, which is beyond the actual electron configuration of magnesium.

2. To the nearest whole number, what is the mass of one mole of hydrogen iodide?

• A. 2 g/mol
• B. 58 g/mol
• C. 87 g/mol
• D. 128 g/mol

Correct answer: C

Rationale: The molar mass of hydrogen iodide (HI) is the sum of the atomic masses of its constituent elements. Hydrogen (H) has a molar mass of approximately 1 g/mol, and iodine (I) has a molar mass of about 127 g/mol. Thus, the molar mass of hydrogen iodide (HI) is approximately 1 + 127 = 128 g/mol. Rounding to the nearest whole number, the molar mass of hydrogen iodide is 128 g/mol, which is closest to choice C. Choice A (2 g/mol) is too low and does not reflect the correct molar mass of hydrogen iodide. Choice B (58 g/mol) is significantly lower than the actual molar mass. Choice D (128 g/mol) matches the calculated molar mass but is not the nearest whole number as requested.

3. What is the boiling point of water in °C?

• A. 90°C
• B. 100°C
• C. 95°C
• D. 80°C

Correct answer: B

Rationale: The correct answer is 100°C. The boiling point of water in Celsius is 100°C, which is standard at sea level. This is the temperature at which water changes from a liquid to a gas phase under standard atmospheric pressure. Choice A (90°C), Choice C (95°C), and Choice D (80°C) are incorrect because they do not represent the standard boiling point of water at sea level.

4. A chemist takes 100 mL of a 40 g NaCl solution and dilutes it to 1L. What is the concentration (molarity) of the new solution?

• A. 0.04 M NaCl
• B. 0.25 M NaCl
• C. 0.40 M NaCl
• D. 2.5 M NaCl

Correct answer: C

Rationale: Initially, the chemist has 40 g of NaCl in 100 mL of solution. To find the initial molarity, we need to calculate the number of moles of NaCl using the molar mass of NaCl (58.44 g/mol). After dilution to 1 L, the molarity of the new solution can be calculated by dividing the moles of NaCl by the total volume in liters. Therefore, the concentration (molarity) of the new solution is 0.40 M NaCl. Choice A (0.04 M NaCl) is incorrect because it doesn't consider the correct molar concentration after dilution. Choice B (0.25 M NaCl) is incorrect as it also doesn't account for the correct molar concentration post-dilution. Choice D (2.5 M NaCl) is incorrect as it is too concentrated given the initial amount of NaCl and the dilution factor.

5. A radioactive isotope has a half-life of 20 years. How many grams of a 6-gram sample will remain after 40 years?

• A. 8
• B. 6
• C. 3
• D. 1.5

Correct answer: C

Rationale: The half-life of a radioactive isotope is the time it takes for half of the original sample to decay. After each half-life period, half of the initial sample remains. In this case, after the first 20 years, half of the 6-gram sample (3 grams) will remain. After another 20 years (total of 40 years), half of the remaining 3 grams will remain, which is 1.5 grams. Therefore, 3 grams will be left after 40 years. Choice A is incorrect as it doesn't consider the concept of half-life and incorrectly suggests an increase in the sample. Choice B is incorrect as it assumes no decay over time. Choice D is incorrect as it miscalculates the remaining amount after two half-life periods.

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