[ch12]

Hi ...
I just want to know how to calculate the amount needed of sulfuric acid and potassium dichromate to prepare 20 L of  ( 0.003 M potassium dichromate + 1 M sulfuric acid ) solution mixture ?? should I use an equal amount of both of them i.e. 10 L of 1 M sulfuric acid and 10 L of 0.003 M potassium dichromate?

[billnotgatez]

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Potassium dichromate, K₂Cr₂O₇, Molar mass 294.185 g/mol
Sulfuric acid, H₂SO₄, Molar mass 98.079 g/mol

[Arkcon]

should I use an equal amount of both of them i.e. 10 L of 1 M sulfuric acid and 10 L of 0.003 M potassium dichromate?

Nice try, but no, that won't work.  Can you see why?  You want 20 liters, but will you get the correct concentration with your mix?  How will you fix the error that results?