Interactions of matter

Question

Determine what mass of Potassium Dichromate is needed to create a 0.409 M solution with a total volume of 0.75 L. 



Answer 1

To create one litre of 1M solution of K2Cr2O7 (Potassium Dichromate) requires one mole of the compound in 1L of solution. The mass of 1 mole is 294.185 g. This can be obtained by adding the atomic masses for each of elements in the formulaic proportion.

To create a 1M solution, we need 294.185 g of the compound dissolved in 1L of solution

To create a 0.409M solution, we need 0.409 * 294.185g (=120.322g) of compound dissolved in 1L of solution.

To create only 0.75L of the 0.409M solution, the amount of compound must also be reduced proportionally, i.e. 0.75*120.322 (=90.241 g)