Q150CP - Chemistry: Molecular Nature Of Matter And Change

Question

Boron trifluoride is used as a catalyst in the synthesis of organic compounds. When this compound is analyzed by mass spectrometry (see Tools of the Laboratory, p. 55), several different 1+ ions form, including ions representing the whole molecule as well as molecular fragments formed by the loss of one, two, and three F atoms. Given that boron has two naturally occurring isotopes, ¹⁰B and ¹¹B, and fluorine has one, ¹⁹F, calculate the masses of all possible 1+ ions.

Step-by-Step Solution

Answer

The masses of all possible 1+ ions are 48 and 49 am respectively

Step 1: Calculating the mass of BF 3

It can be denoted as,

$$\begin{gathered} \mathbf{Molecular}\mathbf{ }\mathbf{mass}\mathbf{ }\mathbf{of}\mathbf{ }{\mathbf{BF}}_{\mathbf{3}}\mathbf{=}\mathbf{1}\mathbf{\times }\mathbf{Atomic}\mathbf{ }\mathbf{mass}\mathbf{ }{\mathbf{of}}^{\mathbf{10}}\mathbf{B}\mathbf{+}\mathbf{3}\mathbf{\times }\mathbf{ }\mathbf{Atomic}\mathbf{ }\mathbf{mass}\mathbf{ }{\mathbf{of}}^{\mathbf{19}}\mathbf{F} \\ \mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{=}\mathbf{1}\mathbf{\times }\mathbf{10}\mathbf{+}\mathbf{3}\mathbf{\times }\mathbf{19} \\ \mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{=}\mathbf{67} \end{gathered}$$

On losing one of the F- ion the mass will be 48 amu.

Step 2: Calculating another mass of BF 3

Then,

$\mathbf{Molecular}\mathbf{ }\mathbf{mass}\mathbf{ }\mathbf{of}\mathbf{ }{\mathbf{BF}}_{\mathbf{3}}\mathbf{=}\mathbf{1}\mathbf{\times }\mathbf{Atomic}\mathbf{ }\mathbf{mass}\mathbf{ }{\mathbf{of}}^{\mathbf{11}}\mathbf{B}\mathbf{+}\mathbf{3}\mathbf{\times }\mathbf{Atomic}\mathbf{ }\mathbf{mass}\mathbf{ }{\mathbf{of}}^{\mathbf{19}}\mathbf{F}\mathbf{ }$

On losing one of the F- ion the mass will be 49amu.