The molecular weight of PCl3 is blank amu.
The correct answer and explanation is:
The molecular weight of PCl₃ is 137.33 amu.
To find the molecular weight of phosphorus trichloride (PCl₃), one must calculate the sum of the atomic masses of all the atoms in a single molecule of the compound. A molecule of PCl₃ consists of one atom of phosphorus (P) and three atoms of chlorine (Cl).
From the periodic table:
- The atomic mass of phosphorus (P) is approximately 30.97 amu
- The atomic mass of chlorine (Cl) is approximately 35.45 amu
Since there are three chlorine atoms in PCl₃, multiply the atomic mass of chlorine by 3:
35.45 amu × 3 = 106.35 amu
Now add the atomic mass of phosphorus to the total mass of the three chlorine atoms:
30.97 amu + 106.35 amu = 137.32 amu
Due to rounding, the final molecular weight is typically reported as 137.33 amu
The molecular weight, also known as molecular mass, is essential in chemistry because it allows scientists to convert between grams and moles of a substance using the concept of the mole. One mole of PCl₃ would weigh 137.33 grams. This is useful in stoichiometric calculations, where balanced chemical equations are used to predict the amounts of reactants and products in chemical reactions.
Understanding molecular weight also plays a role in determining physical properties like boiling point, vapor pressure, and solubility. Phosphorus trichloride is a colorless, fuming liquid with a sharp odor. It is used in organic synthesis and industrial applications. Its relatively high molecular weight contributes to its stability and reactivity as a chlorinating agent. Calculating its molecular weight helps in handling it safely and effectively in chemical processes.