Final answer:
To calculate the molar mass of (NH4)3PO4, add together the atomic masses of nitrogen, hydrogen, phosphorus, and oxygen according to the number of each atom in the compound, resulting in a total of 149.12 amu.
Step-by-step explanation:
Calculating Molar Mass
To calculate the molar mass of (NH4)3PO4, you must add the atomic masses of all the atoms in the formula. In one molecule of (NH4)3PO4, there are three ammonium ions (NH4)+ and one phosphate ion (PO4)3-. The atomic masses (rounded to two decimal places) are approximately: N (14.01 amu), H (1.01 amu), P (30.97 amu), and O (16.00 amu). The molar mass calculation would be:
- (3 moles N × 14.01 amu/mole) + (12 moles H × 1.01 amu/mole) + (1 mole P × 30.97 amu/mole) + (4 moles O × 16.00 amu/mole)
- (42.03 amu) + (12.12 amu) + (30.97 amu) + (64.00 amu)
- This gives a total molar mass of 149.12 amu.
The molar mass is essential for converting between moles and grams because it acts as a conversion factor. The number of moles multiplied by the molar mass yields grams of the substance. Conversely, grams divided by the molar mass gives the number of moles.
For instance, to calculate the formula mass of other compounds such as Ca3(PO4)2 or H2O, you would use the same process, finding the sum of the atomic masses multiplied by the number of each type of atom present in the compound.
Example: To find the formula mass of H2O, multiply the atomic mass of hydrogen by 2 and add the atomic mass of oxygen, resulting in (2 × 1.01 amu) + (16.00 amu) = 18.02 amu.