To find the molar mass of phosphorus trichloride (PCl3), you need to add the atomic masses of each element in the compound, taking into account the number of atoms of each element present.
Here's how to do it:
-
Identify the elements and their atomic masses:
- Phosphorus (P) has an atomic mass of approximately 30.97 grams per mole (g/mol).
- Chlorine (Cl) has an atomic mass of approximately 35.45 g/mol.
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Determine the number of atoms of each element:
- In PCl3, there is 1 phosphorus atom and 3 chlorine atoms.
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Calculate the molar mass:
- Multiply the atomic mass of each element by the number of atoms present:
- Phosphorus: 1 atom * 30.97 g/mol = 30.97 g/mol
- Chlorine: 3 atoms * 35.45 g/mol = 106.35 g/mol
- Add the results together: 30.97 g/mol + 106.35 g/mol = 137.32 g/mol
- Multiply the atomic mass of each element by the number of atoms present:
Therefore, the molar mass of PCl3 is approximately 137.32 g/mol. This value may vary slightly depending on the periodic table used and the number of decimal places to which the atomic masses are rounded. As noted in the provided video reference, if your periodic table rounds differently, you might get a slightly different answer.
| Element | Atomic Mass (g/mol) | Number of Atoms | Calculation (g/mol) |
|---|---|---|---|
| Phosphorus | 30.97 | 1 | 30.97 |
| Chlorine | 35.45 | 3 | 106.35 |
| Total | 137.32 |
