Question

Question #802e7

Answer 1

Dissolve 24.0 g of `"NaH"_2"PO"_4` in enough distilled water to make 1 L of solution.

Explanation:

Let's say you want to prepare 1 L of 0.200 mol/L solution from solid `"NaH"_2"PO"_4`.

That means you want to add 0.200 mol of the solid to enough water to make 1 L.

The molar mass of `"NaH"_2"PO"_4` is 119.98 g/mol.

So, you would measure out

`0.200 color(red)(cancel(color(black)("mol NaH"_2"PO"_4 )))× ("119.98 g NaH"_2"PO"_4)/(1 color(red)(cancel(color(black)("mol NaH"_2"PO"_4)))) = "24.0 g NaH"_2"PO"_4`.

You would transfer this carefully to a 1 L volumetric flask and use about 500 mL of distilled water to dissolve the solid.

Then you would add enough more distilled water to make the volume up to the 1 L mark.