The molecular weight of Sodium orthoarsenite (Na_{3}AsO_{3}) is 191.88910284.

Sodium orthoarsenite [Na_{3}AsO_{3}] is an inorganic compound of three elements: Sodium (Na), Arsenic (As), and Oxygen (O). The molecular weight of Sodium orthoarsenite is 191.88910284 which can be calculated by adding up the total weight (atomic weight multiplied by their number) of all its elements.

**CALCULATION PROCEDURE: Sodium orthoarsenite [Na**_{3}AsO_{3}] Molecular Weight Calculation

_{3}AsO

_{3}] Molecular Weight Calculation

**Step 1: Find out the chemical formula and determine constituent atoms and their number in a Sodium orthoarsenite molecule. **You will know different atoms and their number in a Sodium orthoarsenite molecule from the chemical formula. The chemical formula of Sodium orthoarsenite is Na

_{3}AsO

_{3}. From the chemical formula, you can find that one molecule of Sodium orthoarsenite has three Sodium (Na) atoms, one Arsenic (As) atom, and three Oxygen (O) atoms.

**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 Arsenic (As): 74.921595 (Ref: Jlab-ele033, ciaaw-arsenic)

Atomic weight of Oxygen (O): 15.9994 (Ref: Jlab-ele008)

**Step 3: Calculate the molecular weight of Sodium orthoarsenite by adding the total weight of all atoms. **

Number of Sodium (Na) atoms in Sodium orthoarsenite: 3

Atomic weight of Sodium: 22.98976928

Total weight of Sodium atoms in Sodium orthoarsenite: 22.98976928 x 3 = 68.96930784

Number of Arsenic (As) atoms in Sodium orthoarsenite: 1

Atomic weight of Arsenic: 74.921595

Total weight of Arsenic atoms in Sodium orthoarsenite: 74.921595 x 1 = 74.921595

Number of Oxygen (O) atoms in Sodium orthoarsenite: 3

Atomic weight of Oxygen: 15.9994

Total weight of Oxygen atoms in Sodium orthoarsenite: 15.9994 x 3 = 47.9982

**Step 4: Calculate the molecular weight of Sodium orthoarsenite by adding up the total weight of all atoms. **

Molecular weight of Sodium orthoarsenite : 68.96930784 (Sodium) + 74.921595 (Arsenic) + 47.9982 (Oxygen) = 191.88910284

So the molecular weight of Sodium orthoarsenite is 191.88910284.

Sodium orthoarsenite [Na_{3}AsO_{3}] Molecular Weight Calculation

Molecular weight of Sodium orthoarsenite (Na_{3}AsO_{3}) | |||

Constituent atoms | Number of each atom | Atomic weight | Total weight |

Sodium (Na) | 3 | 22.98976928 | 68.96930784 |

Arsenic (As) | 1 | 74.921595 | 74.921595 |

Oxygen (O) | 3 | 15.9994 | 47.9982 |

Molecular weight of Sodium orthoarsenite (Na_{3}AsO_{3}): | 191.88910284 |

## REFERENCES:

- Ciaaw-sodium : https://www.ciaaw.org/sodium.htm
- Jlab-ele033: https://education.jlab.org/itselemental/ele033.html
- ciaaw-arsenic: https://www.ciaaw.org/arsenic.htm
- Jlab-ele008: https://education.jlab.org/itselemental/ele008.html

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