What is the molar mass of boron (B)?
A. 5 g/mol
B. 10.81 g
O C. 10.81 g/mol
D. 5 g
The Correct Answer and Explanation is :
The correct answer is C. 10.81 g/mol.
Explanation:
The molar mass of an element refers to the mass of one mole of its atoms, and it is typically expressed in grams per mole (g/mol). To determine the molar mass of boron (B), we need to refer to its atomic mass, which is listed on the periodic table.
- Boron has an atomic number of 5, meaning it has 5 protons in its nucleus.
- The atomic mass of boron is approximately 10.81 u (atomic mass units), which is the weighted average of the masses of all naturally occurring isotopes of boron. This value is rounded to 10.81 g/mol for practical use in calculations involving moles.
Since atomic mass is measured in unified atomic mass units (u), and 1 u is equivalent to 1 g/mol, the atomic mass of boron is directly equal to its molar mass of 10.81 g/mol. Therefore, option C is the correct answer.
Why the other options are incorrect:
- A. 5 g/mol: This is incorrect because the molar mass of boron is much greater than 5 g/mol. The atomic number (5) does not equate to the molar mass.
- B. 10.81 g: This option incorrectly omits the “per mole” aspect. The molar mass must be expressed in units of grams per mole (g/mol), not just grams.
- D. 5 g: This is not a correct choice because the value 5 g does not correspond to the molar mass of boron. It only matches the atomic number.
Thus, C. 10.81 g/mol correctly represents the molar mass of boron, reflecting its atomic mass and providing the correct conversion between atomic mass units and grams per mole.