The molecular weight of Trimethylarsine [(CH_{3})_{3}As] is 120.025695.

Trimethylarsine [(CH_{3})_{3}As] is an organic compound of three elements: Carbon (C), Hydrogen (H), and Arsenic (As). The molecular weight of Trimethylarsine is 120.025695 which can be calculated by adding up the total weight (atomic weight multiplied by their number) of Carbon, Hydrogen, Arsenic, and Oxygen.

**CALCULATION PROCEDURE: Trimethylarsine [(CH**_{3})_{3}As] Molecular Weight Calculation

_{3})

_{3}As] Molecular Weight Calculation

**Step 1: Find out the chemical formula and determine constituent atoms and their number in a Trimethylarsine molecule.**You will know different atoms and their number in a Trimethylarsine molecule from the chemical formula. The chemical formula of Trimethylarsine is [(CH

_{3})

_{3}As]. From the chemical formula, you can find that one molecule of Trimethylarsine has three Carbon (C) atoms, nine Hydrogen (H) atoms, and one Arsenic (As) atom.

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

Atomic weight of Carbon (C): 12.0107 (Ref: Jlab-ele006)

Atomic weight of Hydrogen (H): 1.008 (Ref: Lanl-1)

Atomic weight of Arsenic (As): 74.921595 (Ref: Jlab-ele033, ciaaw-arsenic)

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

Number of Carbon atoms in Trimethylarsine: 3

Atomic weight of Carbon (C): 12.0107

Total weight of Carbon atoms in Trimethylarsine: 12.0107 x 3 = 36.0321

Number of Hydrogen atoms in Trimethylarsine: 9

Atomic weight of Hydrogen (H): 1.008

Total weight of Hydrogen atoms in Trimethylarsine: 1.008 x 9 = 9.072

Number of Arsenic atoms in Trimethylarsine: 1

Atomic weight of Arsenic (As): 74.921595

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

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

Molecular weight of Trimethylarsine: 36.0321 (Carbon) + 9.072 (Hydrogen) + 74.921595 (Arsenic) = 120.025695

So the molecular weight of Trimethylarsine is 120.025695.

**Trimethylarsine [(CH _{3})_{3}As] Molecular Weight Calculation**

Molecular weight of Trimethylarsine [(CH_{3})_{3}As] | |||

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

Carbon (C) | 3 | 12.0107 | 36.0321 |

Hydrogen (H) | 9 | 1.008 | 9.072 |

Arsenic (As) | 1 | 74.921595 | 74.921595 |

Molecular weight of Trimethylarsine [(CH_{3})_{3}As]: | 120.025695 |

## REFERENCES:

- Lanl-1: https://periodic.lanl.gov/1.shtml
- Jlab-ele006; https://education.jlab.org/itselemental/ele006.html
- Jlab-ele033: https://education.jlab.org/itselemental/ele033.html
- ciaaw-arsenic: https://www.ciaaw.org/arsenic.htm

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