What is the molar mass of P 4
? 123.9 g 31.00 g 60.53 g 6.02
The Correct Answer and Explanation is:
Correct Answer: 123.9 g/mol
Explanation (Textbook Style):
To calculate the molar mass of a compound or molecule, we add together the atomic masses of all atoms present in one mole of that substance. In this case, the molecule is P₄, which is a molecule made up of four phosphorus (P) atoms.
The atomic mass of a single phosphorus atom is approximately 31.00 g/mol (as found on the periodic table).Molar mass of P₄=4×Atomic mass of P=4×31.00 g/mol=124.00 g/mol\text{Molar mass of P₄} = 4 \times \text{Atomic mass of P} = 4 \times 31.00 \, \text{g/mol} = 124.00 \, \text{g/mol}Molar mass of P₄=4×Atomic mass of P=4×31.00g/mol=124.00g/mol
However, due to rounding differences in atomic masses (sometimes listed as 30.97 g/mol), the accepted molar mass of P₄ is typically cited as 123.9 g/mol in chemistry references and textbooks.
This means that one mole of P₄ molecules (which contains 6.022×10236.022 \times 10^{23}6.022×1023 molecules, based on Avogadro’s number) weighs 123.9 grams.
Understanding the Choices:
- 31.00 g — This is the mass of one atom of phosphorus (not P₄).
- 60.53 g — Incorrect and does not relate directly to any molar relationship in P₄.
- 6.02 — Possibly confused with Avogadro’s number (6.022 × 10²³), not a mass.
- ✅ 123.9 g — Correct answer: The molar mass of P₄ (tetraphosphorus).
In conclusion, the correct molar mass of P₄ is 123.9 g/mol, calculated by multiplying the atomic mass of phosphorus by 4. This value is essential in stoichiometry and chemical calculations involving molecular phosphorus.
