Question

please show work for each probelm, so I can use to practice. thank you

part 1

Tries remaining 1 Points out of 1.00 P Flag question What is the pH of a solution that contains 0.50 M H3PO4 and 0.89 M NaH2PO4? The K, of H3PO4 is 7.5x10-3 Multiple tries are permitted; however, 20% (1/4) point will be deducted for each incorrect response

part 2

part 3

Answer 1

1)

concentration of H3PO4 = 0.50 M

concentration of NaH2PO4 = 0.89 M

pKa = -log Ka = 2.125

pH = pKa + log [salt / acid]

    = 2.125 + log [NaH2PO4 / H3PO4]

pH = 2.125 + log (0.89 / 0.50)

pH = 2.38

2)

millimoles of NH2Cl = 4.30 x 0.044 = 0.1892

mmoles of NH2Cl = mmoles of HBr

mmoles of HBr = 0.1892

0.074 x V = 0.1892

V = 2.56

volume of titrant = 2.56 mL

3)

moles of HCN = 0.060 x 0.0067 = 4.02 x 10^-4

At equivalence point . salt only remains.

salt concentration = 4.02 x 10^-4 / 0.060 + 0.033

                               = 4.32 x 10^-3 M

pKa = 9.31

pH = 7 + 1/2 (pKa + log C)

      = 7 + 1/2 (9.31 + log 0.00432)

pH = 10.47