Acids
Introductory inorganic acids contain replaceable hydrogen and an acid residue. Their formulas, indicators, and reaction patterns help predict salts, gases, and water formed in common reactions.
Learning goals
- Recognize, classify, and name common acids.
- Distinguish oxygen-containing and oxygen-free acids.
- Predict reactions with metals, bases, basic oxides, and some salts.
- Describe safe preparation principles.
Classification and names
| Group | Examples | Acid residue |
|---|---|---|
| Oxygen-free | HCl, H2S | chloride, sulfide |
| Oxygen-containing | H2SO4, HNO3, H2CO3 | sulfate, nitrate, carbonate |
The number of replaceable hydrogen atoms gives basicity: HCl is monobasic, H2SO4 is dibasic. Do not confuse acid basicity with acid strength; they describe different ideas.
Indicators and reactions
In acidic aqueous solution, blue litmus turns red. An indicator shows an acidic environment, not the exact acid.
| Partner | Typical pattern | Example |
|---|---|---|
| Base | acid + base → salt + water | $HCl+NaOH\rightarrow NaCl+H_2O$ |
| Basic oxide | acid + basic oxide → salt + water | $2HCl+CuO\rightarrow CuCl_2+H_2O$ |
| Active metal | acid + metal → salt + hydrogen | $2HCl+Zn\rightarrow ZnCl_2+H_2\uparrow$ |
| Some salts | gas, precipitate, or weak product drives reaction | $2HCl+Na_2CO_3\rightarrow2NaCl+H_2O+CO_2\uparrow$ |
Use the metal activity series: not every metal displaces hydrogen from a dilute acid. Reaction conditions and acid type also matter.