Calculate the pH of a solution that contains .03 g of NaH2PO4*H2O and .01 g of...

Calculate the pH of a solution that contains .03 g of NaH2PO4*H2O and .01 g of Na2HPO4*7H2O in 10 mLs.

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Expert Solution

Moles of NaH2PO4H2O = mass of it / Molar mass of it

= 0.03 g / ( 138 g/mol) = 0.0002174

Molarity of NaH2PO4.H2O = moles / vol in L ( where V = 10 ml =0.01L)

= ( 0.0002174 /0.01) = 0.02174 M

Na2HPO4.7H2O moles = ( 0.01 g / 268 g/mol)

= 0.0000373

Molarity of Na2HPO4.7H2O = ( 0.0000373 /0.01) = 0.00373

pH = pka + log [ Na2HPO4.7H2O] / [ NaH2PO4.H2O]

= 7.198 + log ( 0.00373 /0.02174) ( where pka of NaH2PO4 is 7.198)

= 6.43

queen_honey_blossom answered 11 months ago

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