A volume of 5oo ml of potassium sodium tartrate solution S1 of c1=0.21mol/l is to prepared. Determine the mass of hydrated potassium sodium tartrate of formula KNaC4H4O6.4H2O needed for this preparation .(molar atomic masses : H=1;C=12;O=16;Na=23;K=39)

Answer 1

How many mols do you need? That's M x L = ?
Then convert that to grams. mols = grams/molar mass. You can calculate molar mass and you know mols from above, solve for grams.