Chemistry 40 Name______________________________
Quiz 4, Fall 08
1.) Complete the following table. (3points)
Acid Base Conjugate Acid Conjugate Base
H2O NH3 NH4+ HO-
HCl H2O H3O+ Cl-
H2SO4 NaOH H2O HSO4-
2.) What is the molarity of a 200ml solution containing 4.2 g of NaCl? (3 points)
Molar Mass of NaCl = 58.443g moles of NaCl = 4.2g / 58.433g = .072 moles
Molarity (M) = moles (n)/ volume (L) = .072 / 200 x 10-3 = .36M
3.) What is the concentration of potassium ions in a 1.4M solution of K2SO4? (2 points)
K2SO4 = 2K+ + SO42-
1.4M x 2 = 2.8M
5.) What is the pH of a 10 - 3 M solution of HCl? (2 points)
pH = 3
6.) What is the [H+] of a solution given pOH = 3.28 (2 points)
pH + pOH = 14
pH = 14 – 3.28 = 10.72
[H+] = 1.9 x 10-11
7.) Calculate the pH of a 40 ml solution containing 1.00 g of nitric acid. (3 points)
Nitric acid = HNO3 HNO3 = H+ + NO3-
Molar Mass of HNO3 = 63.012g moles of HNO3 = 1.00g / 63.012g = .0159 moles
Molarity (M) = moles (n)/ volume (L) = .0159 / 40 x 10-3 = .398M
8.) How many ml of a 0.2 M NaOH solution are required to bring the pH of 20 ml of a 0.4 M HCl solution
to 7.0? (5 points)
At pH = 7 [H+] = [OH-]
Molarity (M) = moles (n)/ volume (L) moles of HCl = 0.4M x 20x10-3 = .008 = moles of NaOH needed
Volume (L) = .008 moles of NaoH / 0.2M = .04 L or 40 ml