The molar mass (mass of one mole) of sodium chloride NaCl is approximately which of the following values?

Introduction / Context:
Molar mass is a fundamental quantity in chemistry that links the mass of a substance to the amount of substance in moles. Being able to calculate the molar mass of a compound from atomic masses is essential for solving stoichiometry problems, preparing solutions and interpreting chemical equations. Sodium chloride NaCl is a very common compound, and this question asks you to choose its molar mass from several close numerical options, testing both your ability to sum atomic masses and your attention to detail.

Given Data / Assumptions:

• The chemical formula is NaCl, one sodium atom and one chlorine atom per formula unit.
• Approximate atomic mass of sodium Na is 23.0 g/mol.
• Approximate atomic mass of chlorine Cl is 35.45 g/mol.
• Molar mass of the compound equals the sum of the molar masses of the atoms in one formula unit.

Concept / Approach:
To calculate the molar mass of NaCl, we simply add the atomic mass of sodium and the atomic mass of chlorine. Because the formula contains only one atom of each element, there is no need to multiply by larger subscripts. The result should be close to 23 plus 35.45, which is 58.45 g/mol. Small differences in the last decimal place arise from rounding atomic masses, so the option closest to 58.45 is the correct answer.

Step-by-Step Solution:
Step 1: Write down the atomic masses to the appropriate number of significant figures. For sodium, use about 22.99 g/mol, often rounded to 23.0 g/mol. For chlorine, use about 35.45 g/mol. Step 2: Add the masses of the sodium and chlorine atoms in one formula unit: 22.99 + 35.45. Step 3: Perform the addition. 22.99 + 35.45 = 58.44 g/mol to two decimal places. Step 4: Compare the computed value 58.44 g/mol with the options provided. Step 5: Select 58.44 g/mol as it exactly matches the standard molar mass of NaCl to two decimal places.

Verification / Alternative check:
You can cross check the approximate answer by using rounded atomic masses: 23 g/mol for sodium and 35.5 g/mol for chlorine. Their sum is 58.5 g/mol, which is very close to 58.44 g/mol. This confirms that the correct molar mass should be just below 58.5 g/mol, and none of the other options fit this approximate value as well as 58.44 g/mol does. Tables of molar masses used in laboratories and textbooks also list the molar mass of sodium chloride as approximately 58.44 g/mol, providing an independent confirmation.

Why Other Options Are Wrong:
- 57.25 g/mol: This is more than 1 g/mol lower than the calculated molar mass and cannot be correct given the known atomic masses.
- 56.31 g/mol: This value is even further from the actual sum and does not match any reasonable rounding of 23 and 35.45.
- 59.14 g/mol: This is higher than the true value and would require one of the atomic masses to be significantly larger than accepted values.
- 60.00 g/mol: A neat round number that is clearly inconsistent with the sum of 23 and 35.45 and likely included as a distractor.

Common Pitfalls:
A common mistake is to forget that NaCl has only one sodium and one chlorine atom and to accidentally multiply one of the atomic masses by 2. Another error is misreading or misremembering the atomic mass of chlorine, which is about 35.45, not 34 or 36. To avoid such errors, always write out the formula, the atomic masses and the multiplication factors explicitly before adding. Checking that your result is close to a rough mental estimate is also a good habit in multiple choice calculations.

Final Answer:
The molar mass of sodium chloride NaCl is approximately 58.44 g/mol.