In: Chemistry
1) If one liter of nitric acid solution (pH = 1.000) is mixed
with nine liters of barium
hydroxide solution (pH = 11.000), what will be the pH of the
resulting solution?
2) The pH of a 0.10M solution of barium acetate is:_______
1 L of HNO3 , pH = 1.00
[H+] = 10-1
[HNO3] = 0.1 M or 0.1 mol / 1000 mL
Ba(OH)2 , pH = 11.00
pOH = 14 - 11 = 3.0
[OH-] = 10-3
[OH-] = 0.001 M or 0.001 mol/1000 mL
1 mol of Ba(OH)2 contains 2 mol of [OH-]
So0 concentration of Ba(OH)2 = 0.0005 M or 0.0005 mol / 1000 mL
Total moles of Ba(OH)2 = (0.0005 mol / 1 L) * 9 L => 0.0045 mol of Ba(OH)2
And total moles of [OH-] = 0.009 mol
After neutralization H+ + OH- ---> H2O
moles of [H+] = 0.1 - 0.009 => 0.091 moles
Total volume = 1 + 9 = 10 L
[H+] = 0.091 moles / 10 L => 0.0091
pH = - log ( 0.0091)
pH = 2.04
2)
Ba(OAc)2 + 2 H2O ----> 2 AcOH + Ba(OH)2
pH of hydrolized salt composed by strong base and weak acid can be calculated as
pH = 7 + 1/2 pKa + 1/2 log C
pKa of acetic acid = 4.76
C = concentration of salt
C = 2*0.1 = 0.2 M ( after dissociation into water Ba(OAc)2 , it produces 2 eq oa weak acid and 2 eq of OH- ion )
pH = 7 + 1/2 *4.76 + 1/2 log(0.2)
pH = 7 + 2.38 + ( -0.35)
pH = 9.03