Calculate the Molecular mass of phosphorus pentoxide : P2O5. Solution step by step
The correct answer and explanation is:
To calculate the molecular mass of phosphorus pentoxide (P₂O₅), we follow these step-by-step instructions:
Step-by-Step Solution
Step 1: Identify the elements and number of atoms in the compound P₂O₅
- Phosphorus (P) = 2 atoms
- Oxygen (O) = 5 atoms
Step 2: Use the atomic masses from the periodic table
- Atomic mass of Phosphorus (P) = 30.97 g/mol
- Atomic mass of Oxygen (O) = 16.00 g/mol
Step 3: Multiply the atomic mass by the number of atoms for each element
- Phosphorus: 2 × 30.97 = 61.94 g/mol
- Oxygen: 5 × 16.00 = 80.00 g/mol
Step 4: Add the total masses together to get the molecular mass
- Molecular mass of P₂O₅ = 61.94 + 80.00 = 141.94 g/mol
✅ Final Answer:
141.94 g/mol
📘 Explanation (300 Words)
Molecular mass (or molecular weight) is the sum of the atomic masses of all the atoms in a molecule. It is expressed in grams per mole (g/mol) and helps us understand how much one mole of a compound weighs.
In this case, phosphorus pentoxide has the chemical formula P₂O₅, meaning it consists of 2 phosphorus atoms and 5 oxygen atoms bonded together in one molecule.
Using the periodic table, we find the atomic mass of phosphorus is approximately 30.97 g/mol, and oxygen is 16.00 g/mol. These values represent the average mass of an atom of each element, considering all naturally occurring isotopes.
To find the molecular mass:
- Multiply the atomic mass of phosphorus (30.97) by 2 since there are two P atoms, giving 61.94.
- Multiply the atomic mass of oxygen (16.00) by 5 for the five O atoms, giving 80.00.
Adding these two results gives:
61.94 + 80.00 = 141.94 g/mol
This value tells us that one mole of phosphorus pentoxide molecules weighs 141.94 grams. This information is essential in chemical reactions, where accurate amounts of substances are needed for stoichiometry — the calculation of reactants and products in chemical equations.
Thus, knowing the molecular mass of P₂O₅ helps chemists determine how much of it to use or expect in reactions involving phosphorus and oxygen.