Question

You wish to prepare 1 L of a 0.02 Mpotassium iodate solution. You require that the final concentration be within 1% of 0.02 Mand that the concentration must be known precisely to the fourth decimal place. How would you prepare this solution? Specify the glassware you would use, the precision needed for the balance, and the ranges of acceptable masses of KIO3 that can be used.

Short answer

The compound KIO₃should be weighed between 4.237 g and 4.323 g.

Step-by-step solution

Determination of mass of KIO3

We would like to have the desired percentage of 1% of 0.02M. It means that the concentration should be between 0.0918M and 0.0202 M.

So, we should use a 1L volumetric flask for making the solution. They are generally rated at 1%. It should be weighed between 0.0198 mol and 0.0202 mol.

The mass of KIO₃ is,

$$\begin{gathered} \mathbf{mass}\mathbf{=}\mathbf{moles}\mathbf{\times }\mathbf{molar}\mathbf{}\mathbf{mass} \\ \mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{0198}\mathbf{mol}\mathbf{\times }\mathbf{214}\mathbf{.}\mathbf{0}\mathbf{}\mathbf{g}\mathbf{/}\mathbf{mol} \\ \mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{=}\mathbf{4}\mathbf{.}\mathbf{237}\mathbf{g} \end{gathered}$$

$$\begin{gathered} \mathbf{mass}\mathbf{}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{0202}\mathbf{mol}\mathbf{\times }\mathbf{214}\mathbf{.}\mathbf{0}\mathbf{}\mathbf{g}\mathbf{/}\mathbf{mol} \\ \mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{=}\mathbf{4}\mathbf{.}\mathbf{323}\mathbf{g} \end{gathered}$$

Range of acceptable mass of KIO3

The compound KIO₃ should be weighed between 4.237 g and 4.323 g.

Dissolve the compound in the water and dilute it to the mark in a 1.0 L volumetric flask. That will gives the solution within limits.