Concentration Unit Definitions
| Unit | Definition |
|---|---|
| Molarity (M) | moles of soluteliters of solution (mol/L) |
| Molality (m) | moles of solutekg of solvent (mol/kg) |
| Normality (N) | equivalents of soluteliters of solution — N = M × (equivalents per mole) |
| Mass percent (% w/w) | mass of solutemass of solution × 100 |
| Volume percent (% v/v) | volume of solutevolume of solution × 100 |
| ppm (mass basis) | mg solutekg solution — ≈ mg/L for dilute aqueous solutions (ρ ≈ 1) |
| ppb | µg solutekg solution — ≈ µg/L for dilute aqueous solutions |
| Mole fraction (x) | moles of solutetotal moles in solution |
- C1, V1
- Stock concentration and volume
- C2, V2
- Diluted concentration and volume
C1V1 = C2V2
A 1:10 dilution of a stock solution yields 10% of the original concentration; 1:100 yields 1%; 1:1000 yields 0.1%.
Common Concentrated Reagents (Lab Stock)
| Reagent | Typical Assay (% w/w) | Density (g/mL) | Approx. Molarity (M) |
|---|---|---|---|
| Hydrochloric acid, HCl | 37 | 1.19 | ~12.1 |
| Sulfuric acid, H2SO4 | 98 | 1.84 | ~18.4 |
| Nitric acid, HNO3 | 70 | 1.42 | ~15.8 |
| Acetic acid (glacial), CH3COOH | 99.7 | 1.05 | ~17.4 |
| Ammonium hydroxide, NH4OH | 28–30 (as NH3) | 0.90 | ~14.8 |
| Sodium hydroxide (aq. stock), NaOH | 50 | 1.53 | ~19.1 |
| Phosphoric acid, H3PO4 | 85 | 1.685 | ~14.6 |
| Hydrofluoric acid, HF | 49 | 1.15 | ~28.1 |
Hydrofluoric acid requires specific handling procedures and PPE (including calcium gluconate gel on-site) — treat the table value as a reference only, not a handling guide.
pH Quick Reference
| Substance | Approx. pH |
|---|---|
| Battery acid (H2SO4) | ~0.5 |
| Gastric acid | 1.5–3.5 |
| Lemon juice | 2.0–2.6 |
| Vinegar | 2.4–3.4 |
| Orange/apple juice | 3.3–4.0 |
| Black coffee | ~5.0 |
| Pure water (25°C) | 7.0 |
| Human blood | 7.35–7.45 |
| Seawater | 7.5–8.4 |
| Baking soda solution | ~8.3 |
| Milk of magnesia | ~10.5 |
| Household ammonia | 11.0–11.5 |
| Bleach | ~12.5 |
| Sodium hydroxide, 1 M | ~14 |