The molecular weight of Sodium phosphate monobasic monohydrate [NaH₂PO₄.H₂O] is 137.992531278.

Sodium phosphate monobasic (NaH₂PO₄), also called Monosodium phosphate or monobasic monohydrate sodium phosphate, is an inorganic compound of four elements: Sodium, Hydrogen, Phosphorus, and Oxygen. The monohydrate form of Sodium phosphate monobasic monohydrate (NaH₂PO₄.1H₂O) also contains 1 water molecule. The molecular weight of Sodium phosphate monobasic monohydrate is 137.992531278 which can be calculated by adding up the total weight (atomic weight multiplied by their number) of all its elements and water molecule.

CALCULATION PROCEDURE: Sodium phosphate monobasic monohydrate  [NaH₂PO₄.H₂O] Molecular Weight Calculation

Step 1: Find out the chemical formula and determine constituent atoms and their number in a Sodium phosphate monobasic monohydrate molecule.
From the chemical formula, you will know different atoms and their number in a Sodium phosphate monobasic monohydrate molecule. The chemical formula of Sodium phosphate monobasic monohydrate is NaH₂PO₄.H₂O. From the chemical formula of Sodium phosphate monobasic monohydrate, you can find that one molecule of Sodium phosphate monobasic monohydrate consists of one Sodium (C) atom, two Hydrogen (H) atoms, one Phosphorus (P) atom, four Oxygen atoms, and 1 water molecule.

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)
Molecular weight of Water [H2O]: 18.0154

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

Number of Sodium atoms in Sodium phosphate monobasic monohydrate: 1
Atomic weight of Sodium (Na): 22.98976928
Total weight of Sodium atoms in Sodium phosphate monobasic monohydrate: 22.98976928 x 1 = 22.98976928

Number of Hydrogen atoms in Sodium phosphate monobasic monohydrate: 2
Atomic weight of Hydrogen (H): 1.008
Total weight of Hydrogen atoms in Sodium phosphate monobasic monohydrate: 1.008 x 2 = 2.016

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

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

Number of water (H₂O) molecules in Sodium phosphate monobasic monohydrate: 1
Molecular weight of water: 18.0154
Total weight of water in Sodium phosphate monobasic monohydrate: 18.0154 x 1 = 18.0154

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

Molecular weight of Sodium phosphate monobasic monohydrate: 22.98976928 (Sodium) + 2.016 (Hydrogen) + 30.973761998 (Phosphorus) + 63.9976 (Oxygen) + 18.0154 (water)= 137.992531278

So the molecular weight of Sodium phosphate monobasic monohydrate is 137.992531278.

Sodium phosphate monobasic monohydrate [NaH₂PO₄.H₂O] 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
  

See also:

• Hydrogen chloride molecular weight calculation