Answer:
a) pH = 13.447
b) pH = 13.176
Explanation:
Ba (OH)₂ is a strong base and ionizes completely in solution to give barium amend hydroxide ions.
The equation of the dissociation of Ba(OH)₂ is given below:
Ba(OH)₂ ----> Ba2+ + 2OH-
1 mole of Ba(OH)₂ produces 2 Moles of OH- ions
a) Before the addition of HCl, i.e.,when 0.00 mL of HCl has been added;
Concentration of hydroxide ions, [OH-] = 0.140 x 2 = 0.a) [OH-] = 0.100 x 2 = 0.280
pOH = -log [OH-]
pOH = -log (0.280)
pOH = 0.553
pH = 14 - 0.553= 13.447
b) pH when 15.0 mL HCl has been added
Moles Ba(OH)₂ = concentration × volume
Volume of Ba(OH)₂ = 82.0 mL = 0.082 L, concentration = 0.140 M
moles of Ba(OH)₂ = 0.082 x 0.140 = 0.01148 moles
moles OH- produced by 0.01148 moles of Ba(OH)₂ = 2 x 0.01148= 0.02296
moles HCl = 0.0150 L x 0.560 = 0.0084
moles of H+ produced by 0.0084 HCl = 0.0084
0.0084 H+ willnreact with 0.0084 moles of OH-
moles OH- left after the reaction = 0.02296 - 0.0084 = 0.01456 moles
total volume of new solution = (82 +15) mL = 97 mL => 0.097 L
Concentration of OH- ions = moles / volume
[OH-] = 0.01456 / 0.097 = 0.1501
pOH = -log [OH-]
pOH = -log (0.150)
pOH = 0.824
pH = 14 - 0.824
pH = 13.176
