Question

What is the mass of one molecule of yellow phosphorus? (Atomic mass,P = 30).
A. \[1.993 \times {10^{ - 22}}kg\]
B. \[1.993 \times {10^{ - 19}}mg\]
C. \[4.983 \times {10^{ - 20}}mg\]
D. \[4.983 \times {10^{ - 23}}kg\]

Answer 1

Hint: The yellow phosphorus is a chemical compound containing four phosphorus atoms which are together joined to form a tetrahedral arrangement. 1 mole of any substance contains $6.022 \times {10^{23}}$ unit which can be for atoms, molecules, ions.

Complete step by step answer:
Given,
The atomic mass of phosphorus is 30.
The yellow phosphorus has the chemical formula \[{P_4}\]. The yellow phosphorus \[{P_4}\] is formed of four phosphorus atoms arranged in a tetrahedral form.
STEP 1: First we need to find out the molecular weight of yellow phosphorus \[{P_4}\].
The molecular mass is calculated by adding the atomic weight of the atoms and multiplying the number of atoms with it.
The molar mass of \[{P_4}\] = \[4 \times 30\]
The molar mass of \[{P_4}\] = \[120\]
STEP 2: Calculate the mass of yellow phosphorus in one molecule.
One molecule of yellow phosphorus contains four phosphorus atoms.
The Avagadro’s number is the unit in one mole of any substance also stated as molecular weight in grams equal to $6.022 \times {10^{23}}$.
The mass of 1 molecule of yellow phosphorus is calculated by dividing the molecular weight of the yellow phosphorus with the Avagadro’s number.
The mass of one molecule of yellow phosphorous.is calculated as shown below.
\[ \Rightarrow 1\;molecule = \dfrac{{120}}{{6.023 \times {{10}^{23}}}}\]
\[ \Rightarrow 1\;molecule = 1.9923 \times {10^{ - 24}}g\]
\[ \Rightarrow 1\;molecule = 1.9923 \times {10^{ - 19}}mg\]
Thus, 1 molecule of yellow phosphorus contains $1.9923 \times {10^{ - 19}}mg$ mass.

So, the correct answer is Option B.

Note: The property of Avagadro’s number is that the mass of 1 mole substance is the same to the molar mass of the substance. The number of molecules is calculated by multiplying moles by Avagadro’s number.