Recognise and balance carbon, sulfur and nitrogen oxide equations producing acidity.
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Method and worked examples
Carbon dioxide dissolves and participates in CO2+H2O ⇌ H2CO3, followed by acid ionisation. These equilibria help explain ordinary rain’s slight acidity. Sulfur dioxide is commonly represented by SO2+H2O ⇌ H2SO3. Oxidation can also give 2SO2+O2→2SO3, followed by SO3+H2O→H2SO4. These simplified equations summarise chemical changes rather than every atmospheric step.
An overall nitrogen-oxide route is 4NO2+O2+2H2O→4HNO3. The acids donate protons to water, forming H3O+. For example HNO3+H2O→H3O++NO3−. Balance all atoms and charge, and do not confuse sulfurous acid H2SO3 with sulfuric acid H2SO4. Hydrogen-ion increases lower pH on the logarithmic scale.
Example 1
Combine SO2 oxidation and SO3 hydration to give an overall sulfuric-acid equation.
2SO2+O2→2SO3 and 2SO3+2H2O→2H2SO4 combine to 2SO2+O2+2H2O→2H2SO4.
Example 2
Write carbonic acid donating its first proton to water.
H2CO3+H2O ⇌ H3O++HCO3−. Atom counts and total charge are conserved.
Watch out:Their element identities differ: the simplified products include H2CO3 and H2SO3 respectively.
Acid-rain reaction equations practice | Year 11 Chemistry | Ascent Arcade