Question

In: Chemistry

Design a procedure to prepare 75 ml of 0.10 M potassium dihydrogen phosphate solution (KH2PO4) and...

Design a procedure to prepare 75 ml of 0.10 M potassium dihydrogen phosphate solution (KH2PO4) and 75 ml of 0.10 M dipotassium hydrogen phosphate solution (K2HPO4) from the solids. (Hint: What mass of the above solids is required to make 75 ml of a 0.10 M solution?)

Solutions

Expert Solution

75 ml of 0.1M KH2PO4

molar mass of KH2PO4 is 136

no of moles = molarity * volume in L

                  = 0.1*0.075 = 0.0075 moles

mass of KH2PO4 = no of moles * gram molar mass

                          = 0.0075*136 = 1.02gm

One can prepare a 100ml solution of 0.1M KH2PO4 by dissolving 1.36gm of KH2PO4 in a volumetric flask and making up the vlume chances of any error be less than making 75ml of solution.

75 ml of 0.1M of K2HPO4

molar mass of K2HPO4 is 174

no of moles of K2HPO4 = molarity* volume in L

                                    = 0.1* 0.075 = 0.0075 moles

mass of K2HPO4 = no of moles * gram molar mass

                            = 0.0075*174 = 1.305 gm of K2HPO4

Same as above making a 100 ml 0.1 M K2HPO4 solution with 1.74 gm of K2HPO4 in 100 ml volumetric flask would reduce chances of error

                            



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