Here's how to calculate the molar mass of PH₃ (phosphine):

* Find the atomic masses:

* Phosphorus (P): 30.97 g/mol

* Hydrogen (H): 1.01 g/mol

* Multiply the atomic masses by the number of atoms in the molecule:

* Phosphorus: 1 atom * 30.97 g/mol = 30.97 g/mol

* Hydrogen: 3 atoms * 1.01 g/mol = 3.03 g/mol

* Add the results together:

* 30.97 g/mol + 3.03 g/mol = 34.00 g/mol

Therefore, the molar mass of PH₃ is 34.00 g/mol.