The molecular weight of Arsenic acid [H_{3}AsO_{4}] is 141.943195.

Arsenic acid [H_{3}AsO_{4}] is an inorganic compound of three elements: Hydrogen (H), Arsenic (As), and Oxygen (O). The molecular weight of Arsenic acid is 141.943195 which can be calculated by adding up the total weight (atomic weight multiplied by their number) of Hydrogen, Arsenic, and Oxygen.

**CALCULATION PROCEDURE: Arsenic acid [H**_{3}AsO_{4}] Molecular Weight Calculation

_{3}AsO

_{4}] Molecular Weight Calculation

**Step 1: Find out the chemical formula and determine constituent atoms and their number in an Arsenic acid molecule.**You will know different atoms and their number in an Arsenic acid molecule from the chemical formula. The chemical formula of Arsenic acid is [H

_{3}AsO

_{4}]. From the chemical formula, you can find that one molecule of Arsenic acid has three Hydrogen (H) atoms, one Arsenic (As) atom, and four Oxygen (O) atoms.

**Step 2: Find out the atomic weights of each atom (from the periodic table). **Atomic weight of Hydrogen (H): 1.008 (Ref: Lanl-1)

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 total weight of each atom in an Arsenic acid molecule by multiplying its atomic weight by its number.**

Number of Hydrogen atoms in Arsenic acid: 3

Atomic weight of Hydrogen (H): 1.008

Total weight of Hydrogen atoms in Arsenic acid: 1.008 x 3 = 3.024

Number of Arsenic atoms in Arsenic acid: 1

Atomic weight of Arsenic (As): 74.921595

Total weight of Arsenic atoms in Arsenic acid: 74.921595 x 1 = 74.921595

Number of Oxygen atoms in Arsenic acid: 4

Atomic weight of Oxygen (O): 15.9994

Total weight of Oxygen atoms in Arsenic acid: 15.9994 x 4 = 63.9976

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

Molecular weight of Arsenic acid: 3.024 (Hydrogen) + 74.921595 (Arsenic) + 63.9976 (Oxygen) = 141.943195

So the molecular weight of Arsenic acid is 141.943195.

**Arsenic acid [H _{3}AsO_{4}] Molecular Weight Calculation**

Molecular weight of Arsenic acid [H_{3}AsO_{4}] | |||

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

Hydrogen (H) | 3 | 1.008 | 3.024 |

Arsenic (As) | 1 | 74.921595 | 74.921595 |

Oxygen (O) | 4 | 15.9994 | 63.9976 |

Molecular weight of Arsenic acid [H_{3}AsO_{3}]: | 141.943195 |

## REFERENCES:

- Lanl-1: https://periodic.lanl.gov/1.shtml
- Jlab-ele008: https://education.jlab.org/itselemental/ele008.html
- Jlab-ele033: https://education.jlab.org/itselemental/ele033.html
- ciaaw-arsenic: https://www.ciaaw.org/arsenic.htm

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