What are Acids and Bases?
Acids
- • Donate hydrogen ions (H⁺)
- • Taste sour (like lemon juice)
- • pH less than 7
- • Turn litmus paper red
- • Examples: HCl, H₂SO₄, CH₃COOH
Bases
- • Accept hydrogen ions (H⁺)
- • Taste bitter, feel slippery
- • pH greater than 7
- • Turn litmus paper blue
- • Examples: NaOH, Ca(OH)₂, NH₃
The pH Scale
0
7
14
Acidic (pH 0-7)
More H⁺ ions than OH⁻ ions
Battery acid (0), Lemon juice (2), Coffee (5)
Neutral (pH 7)
Equal H⁺ and OH⁻ ions
Pure water (7)
Basic (pH 7-14)
More OH⁻ ions than H⁺ ions
Baking soda (9), Ammonia (11), Bleach (13)
Neutralization Reactions
General Pattern:
Acid + Base → Salt + Water
HCl + NaOH → NaCl + H₂O
What Happens:
- • H⁺ from acid combines with OH⁻ from base
- • Forms water (H₂O)
- • Remaining ions form a salt
- • pH moves toward 7 (neutral)
Common Examples:
HCl + NaOH → NaCl + H₂O
H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O
HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O
Types of Acid-Base Reactions
Strong Acid + Strong Base
Complete neutralization - pH = 7 at equivalence point
HCl + NaOH → NaCl + H₂O
Strong Acids:
HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄
Strong Bases:
NaOH, KOH, Ca(OH)₂, Ba(OH)₂
Weak Acid + Strong Base
pH > 7 at equivalence point (slightly basic)
CH₃COOH + NaOH → CH₃COONa + H₂O
Why pH > 7?
The salt formed can act as a weak base, making the solution slightly basic.
Strong Acid + Weak Base
pH < 7 at equivalence point (slightly acidic)
HCl + NH₃ → NH₄Cl
Why pH < 7?
The salt formed can act as a weak acid, making the solution slightly acidic.
Predicting Products
3-Step Method:
Step 1
Identify the acid (H⁺ donor) and base (H⁺ acceptor)
Step 2
Combine the remaining ions to form the salt
Step 3
H⁺ + OH⁻ → H₂O (water is always formed)
Example: HBr + Ca(OH)₂ → ?
Identify:
HBr = acid
Ca(OH)₂ = base
Ca(OH)₂ = base
Form Salt:
Ca²⁺ + Br⁻
= CaBr₂
= CaBr₂
Add Water:
2HBr + Ca(OH)₂
→ CaBr₂ + 2H₂O
→ CaBr₂ + 2H₂O
Practice Acid-Base Reactions
Use our tools to practice balancing acid-base equations and predicting products!