The molar mass of Ammonium Hydrogen Phosphate; (NH4H2PO4) is? A. 422 g/mole B. 132.1 g/mole C. 164.0 g/mole D. 130.0 g/mole E. 264.2 g/mole F. 123.0 g/mole
The Correct Answer and Explanation is:
To determine the molar mass of ammonium hydrogen phosphate, given the correct formula (NH₄)₂HPO₄, we must add the atomic masses of all atoms present in the compound.
Break the formula down into its components:
- Two ammonium ions: (NH₄)₂
- One hydrogen phosphate ion: HPO₄
Let’s calculate each component step by step using standard atomic masses:
- Nitrogen (N): 14.01 g/mol
- Hydrogen (H): 1.008 g/mol
- Phosphorus (P): 30.97 g/mol
- Oxygen (O): 16.00 g/mol
Ammonium (NH₄):
- One nitrogen: 14.01 g/mol
- Four hydrogens: 4 × 1.008 = 4.032 g/mol
- Total for NH₄: 14.01 + 4.032 = 18.042 g/mol
- Since there are two ammonium ions: 2 × 18.042 = 36.084 g/mol
Hydrogen phosphate (HPO₄):
- One hydrogen: 1.008 g/mol
- One phosphorus: 30.97 g/mol
- Four oxygens: 4 × 16.00 = 64.00 g/mol
- Total for HPO₄: 1.008 + 30.97 + 64.00 = 95.978 g/mol
Add everything together:
- 36.084 (from ammonium)
- 95.978 (from hydrogen phosphate)
- Total molar mass = 36.084 + 95.978 = 132.062 g/mol
Rounded appropriately based on significant figures, the molar mass is 132.1 g/mol, which matches option B.
This compound is often used in fertilizers and buffer solutions in biochemistry. The accuracy in calculating its molar mass is essential for preparing solutions with correct concentrations, especially in experiments where ionic balance and buffering capacity are critical. Proper calculation also helps in determining molarity and stoichiometric requirements during titrations or reactions involving phosphate groups.
