# Phaunouxite [Ca3(AsO4)2.11H2O] Molecular Weight Calculation

The molecular weight of Phaunouxite [Ca3(AsO4)2.11H2O] is 596.24179. Calcium arsenate [Ca3(AsO4)2] is an inorganic compound of three elements: Calcium (Ca), Arsenic (As), and Oxygen (O). The undecahydrate form of Calcium arsenate, Phaunouxite [Ca3(AsO4)2.11H2O], also contains eleven water (H2O) molecules. The molecular weight of Phaunouxite is 596.24179 which can be calculated by adding up the total weight (atomic weight multiplied by their number) of all its elements and water molecules.

# CALCULATION PROCEDURE: Phaunouxite [Ca3(AsO4)2.11H2O] Molecular Weight Calculation

Step 1: Find out the chemical formula and determine constituent atoms and their number in a Phaunouxite molecule.
You will know different atoms and their number in a Phaunouxite molecule from the chemical formula. The chemical formula of Phaunouxite is Ca3(AsO4)2.11H2O. From the chemical formula, you can find that one molecule of Phaunouxite has three Calcium (Ca) atoms, two Arsenic (As) atoms, eight Oxygen (O) atoms, and eleven water molecules.

Step 2: Find out the atomic weights of each atom (from the periodic table).
Atomic weight of Calcium (Ca): 40.078 (Ref: PubChem-20, Ciaaw-calcium)
Atomic weight of Arsenic (As): 74.921595 (Ref: Jlab-ele033, ciaaw-arsenic)
Atomic weight of Oxygen (O): 15.9994 (Ref: Jlab-ele008)
Molecular weight of Water [H2O]: 18.0154

Step 3: Calculate the total weight of each atom in a Phaunouxite molecule by multiplying its atomic weight by its number.

Number of Calcium atoms in Phaunouxite: 3
Atomic weight of Calcium (Ca): 40.078
Total weight of Calcium atoms in Phaunouxite: 40.078 x 3 = 120.234

Number of Arsenic atoms in Phaunouxite: 2
Atomic weight of Arsenic (As): 74.921595
Total weight of Arsenic atoms in Phaunouxite: 74.921595 x 2 = 149.84319

Number of Oxygen atoms in Phaunouxite: 8
Atomic weight of Oxygen (O): 15.9994
Total weight of Oxygen atoms in Phaunouxite: 15.9994 x 8 = 127.9952

Number of water (H2O) molecules in Calcium chloride monohydrate: 11
Molecular weight of water: 18.0154
Total weight of water in Calcium chloride monohydrate: 18.0154 x 11 = 198.1694

Step 4: Calculate the molecular weight of Phaunouxite by adding up the total weight of all atoms.

Molecular weight of Phaunouxite: 120.234 (Calcium) + 149.84319 (Arsenic) + 127.9952 (Oxygen) + 198.1694 (water)= 596.24179

So the molecular weight of Phaunouxite is 596.24179.

Phaunouxite [Ca3(AsO4)2.11H2O] Molecular Weight Calculation

## REFERENCES:

• PubChem-20: https://pubchem.ncbi.nlm.nih.gov/element/20
• Ciaaw-calcium: https://www.ciaaw.org/calcium.htm
• Jlab-ele008: https://education.jlab.org/itselemental/ele008.html
• Jlab-ele033: https://education.jlab.org/itselemental/ele033.html
• https://www.ciaaw.org/arsenic.htm

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