# What is the molar concentration of potassium ion in a solution that is 73*"ppm" with respect to K_3[Fe(C-=N)_6]?

May 18, 2017

$\text{1 ppm}$ specifies $1 \cdot m g \cdot {L}^{-} 1$ of solution.........

#### Explanation:

And thus in $1 \cdot L$ of solution, we have............

$\frac{\frac{73 \times {10}^{-} 3 \cdot g}{329.24 \cdot g \cdot m o {l}^{-} 1}}{1 \cdot L} = 2.21 \times {10}^{-} 5 \cdot m o l \cdot {L}^{-} 1$ with respect to ${K}_{3} \left[F e {\left(C \equiv N\right)}_{6}\right]$.

Since that are 3 moles of potassium ion per mole of salt, $\left[{K}^{+}\right] = 6.7 \times {10}^{-} 5 \cdot m o l \cdot {L}^{-} 1$.

You might be tempted to argue that I should have accounted for the solution density in these calculations. Even if these data were available, at $\text{ppm}$ concentrations they would make negligible difference, and so may be ignored.

If I dissolved $1 \cdot g$ of common salt, $N a C l$, in a $1 \cdot L$ volume of water, what would be the $\text{ppm}$ concentration?