To determine the relative formula mass of the compound [tex]\((NH_4)_3PO_4\)[/tex], we need to follow a step-by-step process:
1. Identify the number of each type of atom in the compound:
- In the compound [tex]\((NH_4)_3PO_4\)[/tex], each [tex]\((NH_4)\)[/tex] unit contains:
- 1 Nitrogen (N) atom
- 4 Hydrogen (H) atoms
- The subscript 3 outside the parentheses indicates there are 3 [tex]\((NH_4)\)[/tex] units, so:
- Number of Nitrogen atoms = 3 units × 1 Nitrogen atom/unit = 3 Nitrogen atoms
- Number of Hydrogen atoms = 3 units × 4 Hydrogen atoms/unit = 12 Hydrogen atoms
- Within the compound formula, [tex]\(PO_4\)[/tex] contains:
- 1 Phosphorus (P) atom
- 4 Oxygen (O) atoms
2. List the atomic masses of each element:
- Nitrogen (N): 14
- Hydrogen (H): 1
- Phosphorus (P): 31
- Oxygen (O): 16
3. Calculate the total mass for each type of atom:
- Total mass of Nitrogen = Number of Nitrogen atoms × Atomic mass of Nitrogen
- Total mass of N = 3 × 14 = 42
- Total mass of Hydrogen = Number of Hydrogen atoms × Atomic mass of Hydrogen
- Total mass of H = 12 × 1 = 12
- Total mass of Phosphorus = Number of Phosphorus atoms × Atomic mass of Phosphorus
- Total mass of P = 1 × 31 = 31
- Total mass of Oxygen = Number of Oxygen atoms × Atomic mass of Oxygen
- Total mass of O = 4 × 16 = 64
4. Sum the masses to get the relative formula mass of [tex]\((NH_4)_3PO_4\)[/tex]:
- Relative formula mass = Total mass of N + Total mass of H + Total mass of P + Total mass of O
- Relative formula mass = 42 + 12 + 31 + 64 = 149
So, the relative formula mass of [tex]\((NH_4)_3PO_4\)[/tex] is 149.
