The question is incomplete, here is the complete question.
A chemist adds 345.0 mL of a 0.0013 mM (MIllimolar) copper(II) fluoride
solution to a reaction flask.
Calculate the mass in micrograms of copper(II) fluoride the chemist has added to the flask. Be sure your answer has the correct number of significant digits.
Answer : The mass of copper(II) fluoride is, 0.13 mg
Explanation : Given,
Millimolarity of copper (II) fluoride = 0.0013 mM
This means that 0.0013 millimoles of copper (II) fluoride is present in 1 L of solution
Converting millimoles into moles, we use the conversion factor:
1 moles = 1000 millimoles
So, ![0.0013mmol\times \frac{1mol}{1000mmol}=1.3\times 10^{-6}mol](https://tex.z-dn.net/?f=0.0013mmol%5Ctimes%20%5Cfrac%7B1mol%7D%7B1000mmol%7D%3D1.3%5Ctimes%2010%5E%7B-6%7Dmol)
To calculate the number of moles, we use the equation:
![\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}](https://tex.z-dn.net/?f=%5Ctext%7BNumber%20of%20moles%7D%3D%5Cfrac%7B%5Ctext%7BGiven%20mass%7D%7D%7B%5Ctext%7BMolar%20mass%7D%7D)
We are given:
Moles of copper (II) fluoride solution = ![1.3\times 10^{-6}mol](https://tex.z-dn.net/?f=1.3%5Ctimes%2010%5E%7B-6%7Dmol)
Molar mass of copper (II) fluoride = 101.5 g/mol
Putting values in above equation, we get:
![1.3\times 10^{-6}mol=\frac{\text{Mass of copper (II) fluoride}}{101.5g/mol}\\\\\text{Mass of copper (II) fluoride}=(1.3\times 10^{-6}mol\times 101.5g/mol)=1.32\times 10^{-4}g](https://tex.z-dn.net/?f=1.3%5Ctimes%2010%5E%7B-6%7Dmol%3D%5Cfrac%7B%5Ctext%7BMass%20of%20copper%20%28II%29%20fluoride%7D%7D%7B101.5g%2Fmol%7D%5C%5C%5C%5C%5Ctext%7BMass%20of%20copper%20%28II%29%20fluoride%7D%3D%281.3%5Ctimes%2010%5E%7B-6%7Dmol%5Ctimes%20101.5g%2Fmol%29%3D1.32%5Ctimes%2010%5E%7B-4%7Dg)
Converting this into milligrams, we use the conversion factor:
1 g = 1000 mg
So,
![\Rightarrow 1.32\times 10^{-4}g\times (\frac{1000mg}{1g})=0.13mg](https://tex.z-dn.net/?f=%5CRightarrow%201.32%5Ctimes%2010%5E%7B-4%7Dg%5Ctimes%20%28%5Cfrac%7B1000mg%7D%7B1g%7D%29%3D0.13mg)
Therefore, the mass of copper(II) fluoride is, 0.13 mg