# Sodium Phosphate Dibasic Dihydrate [Na2HPO4.2H2O] Molecular Weight Calculation

The molecular weight of Sodium phosphate dibasic dihydrate [Na2HPO4.2H2O] is 177.9897.

Sodium phosphate dibasic (Na2HPO4), also called Disodium phosphate (DSP) or disodium hydrogen phosphate, is an inorganic compound of four elements: Sodium, Hydrogen, Phosphorus, and Oxygen. The dihydrate form of Sodium phosphate dibasic (Na2HPO4.2H2O) also contains 2 water molecules. The molecular weight of Sodium phosphate dibasic dihydrate is 177.9897 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: Sodium phosphate dibasic dihydrate  [Na2HPO4.2H2O] Molecular Weight Calculation

Step 1: Find out the chemical formula and determine constituent atoms and their number in a Sodium phosphate dibasic dihydrate molecule.
From the chemical formula, you will know different atoms and their number in a Sodium phosphate dibasic dihydrate molecule. The chemical formula of Sodium phosphate dibasic dihydrate is Na2HPO4.2H2O. From the chemical formula of Sodium phosphate dibasic dihydrate, you can find that one molecule of Sodium phosphate dibasic dihydrate consists of two Sodium (C) atoms, one Hydrogen (H) atom, one Phosphorus (P) atom, four Oxygen atoms, and two water molecules.

Step 2: Find out the atomic weights of each atom (from the periodic table).

Atomic weight of Sodium (Na): 22.98976928 (Ref: Ciaaw-sodium)
Atomic weight of Hydrogen (H): 1.008 (Ref: Lanl-1)

Atomic weight of Oxygen (O): 15.9994 (Ref: Jlab-ele008)
Atomic weight of
Phosphorus (P): 30.973761998 (Ref: Jlab-ele015)

Step 3: Calculate the total weight of each atom in a Sodium phosphate dibasic dihydrate molecule by multiplying its atomic weight by its number.

Number of Sodium atoms in Sodium phosphate dibasic dihydrate: 2
Atomic weight of Sodium (Na): 22.98976928
Total weight of Sodium atoms in Sodium phosphate dibasic dihydrate: 22.98976928 x 2 = 45.97953856

Number of Hydrogen atoms in Sodium phosphate dibasic dihydrate: 1
Atomic weight of Hydrogen (H): 1.008
Total weight of Hydrogen atoms in Sodium phosphate dibasic dihydrate: 1.008 x 1 = 1.008

Number of Phosphorus atoms in Sodium phosphate dibasic dihydrate: 1
Atomic weight of Phosphorus (P): 30.973761998
Total weight of Phosphorus atoms in Sodium phosphate dibasic dihydrate: 30.973761998 x 1 = 30.973761998

Number of Oxygen atoms in Sodium phosphate dibasic dihydrate: 4
Atomic weight of Oxygen (O): 15.9994
Total weight of Oxygen atoms in Sodium phosphate dibasic dihydrate: 15.9994 x 4 = 63.9976

Number of water (H2O) molecules in Sodium phosphate dibasic dihydrate: 2
Molecular weight of water: 18.0154
Total weight of water in Sodium phosphate dibasic dihydrate: 18.0154 x 2 = 36.0308

Step 4: Calculate the molecular weight of Sodium phosphate dibasic dihydrate by adding up the total weight of all atoms.

Molecular weight of Sodium phosphate dibasic dihydrate: 45.97953856 (Sodium) + 1.008 (Hydrogen) + 30.973761998 (Phosphorus) + 63.9976 (Oxygen) + 36.0308 (Water) = 177.9897

So the molecular weight of Sodium phosphate dibasic dihydrate is 177.9897.

Sodium phosphate dibasic dihydrate [Na2HPO4.2H2O] Molecular Weight Calculation

## REFERENCES:

• Lanl-1: https://periodic.lanl.gov/1.shtml
• Ciaaw-sodium: https://www.ciaaw.org/sodium.htm
• Jlab-ele008: https://education.jlab.org/itselemental/ele008.html
•  Jlab-ele015: https://education.jlab.org/itselemental/ele016.html