Acids and Bases
Strengths of Acids and Bases
Making Dilutions
Strengths of Acids and Bases
Strong acids completely ionize (100%) in
aqueous solutions
HCl + H2O
H3O+ + Cl- (100 % ions)
Strong bases completely (100%) dissociate into
ions in aqueous solutions.
NaOH
Na+ (aq) + OH-(aq)
(100 % ions)
NH3, A Bronsted-Lowry Base
When NH3 reacts with water, most of the
reactants remain dissolved as molecules, but a
few NH3 reacts with water to form NH4+ and
hydroxide ion.
NH3
+
acceptor
H2O
NH4+(aq)
+ OH- (aq)
donor
+
+
Strong and Weak
Acids and Bases
Strong acids
HCl, HNO3 , H2SO4
Most other acids are weak.
Strong bases
NaOH, KOH, and Ca(OH)2
Most other bases are weak.
Acid/Base Strength Check
Identify each of the following as a
1) strong acid or base 2) weak acid
3) weak base
A. ___ HCl (aq)
B. ___ NH3(aq)
C. ___ NaOH (aq)
D. ___ H2CO3 (aq)
Solution
Identify each of the following as a
1) strong acid or base 2) weak acid
3) weak base
A. _1__ HCl (aq)
B. _3__ NH3(aq)
C. _1__ NaOH (aq)
D. _2__ H2CO3 (aq)
Antacids
Used to neutralize stomach acid (HCl)
Many contain one or more weak bases
Alka-Seltzer:
NaHCO3, citric acid, and aspirin
Di-gel:
CaCO3 and Mg(OH)2
Gelusil:
Al(OH)3 and Mg(OH)2
Maalox:
Al(OH)3 and Mg(OH)2
Mylanta:
Al(OH)3 and Mg(OH)2
More Antacids
Milk of Magnesia:
Rolaids:
Mg(OH)2
AlNa(OH)2CO3
aluminum sodium dihydroxy carbonate
Tums:
CaCO3
Tempo:
CaCO3, Al(OH)3, Mg(OH)2
Dilutions
 Add water
 Volume increases.
 New concentration is less than initial
Concentration of A Diluted
Solution
A 25 mL sample of a 6.0 M KOH is diluted by
adding 75 mL of water. Calculate the new
concentration of the KOH solution.
Moles KOH = 0.025 L x 6.0 moles = 0.15 moles
1L
New volume = 25 mL + 75 mL = 100. mL = 0.100 L
New molarity = 0.15 moles = 1.5 M
0.100 L
Dilution Calculation
A 125 mL sample of a 3.0 M HCl is diluted
by adding 250 mL of water. The new
concentration of the HCl solution is
1) 8.0 M
2) 1.5 M
3) 1.0 M
Solution
moles HCl = 0.125 L x 3.0 moles = 0.375 mole
1L
new M = 0.375 mole
0.375 L
(new volume)
= 1.0 M HCl
Calculation of Concentration
A 50.0 mL sample of 15% sucrose solution is
diluted by adding 200. mL of water. The new
concentration of the sucrose solution is
1) 3.0 %
2) 7.5 %
3) 10. %
Solution
A 50.0 mL sample of 15% sucrose solution is
diluted by adding 200. mL of water. The new
concentration of the sucrose solution is
1) 3.0 %
g sucrose = 50.0 mL x 15 g sucrose = 7.5 g
100 mL
new % = 7.5 g sucrose
= 3.0 % sucrose
250 mL
(new volume)