Acids: Solid H2SO4 not an acid, when aqueous it is an acid. They ionise into (2)H
+ and SO4
2
. Need
to know acids- HCl, H2SO4, H3PO4, HNO3 and CH3COOH.
• Strong Acid: When dissolved in water, a strong acid completely dissociates in aqueous solution,
releasing H
+
.
• Weak Acid: It partially dissociates in aqueous solution. The equilibrium sign indicates forward
reaction complete.
• Bases: A compound acts as a base when it accepts H+
. Base neutralises acid to form salt and water.
Bases are
– Metal oxides
– Metal hydroxides.
– Metal carbonates.
– Ammonia.
– NOT metals.
• Alkali: An alkali is a base that dissolves in water releasing OHinto solution. NaOH (aq) -> Na+
(aq)
+ OH-
(aq). Need to know alkalis- NaOH, KOH and NH3.
• Why Described as Salt: A salt is when the H+
in an acid is replaced by a metal ion or an ammonium
ion in neutralisation. Name the acid and metal ion. Chloride, sulphate, nitrate and ethanoate salts.
• Can divide moles of alkali reacted with moles of acid reacted, to work out number of H in chemical
formula or H+
ions replaced by metal ions to form salts.
• H4N2O3 made of NH4
+ and NO3
–
ions
• Ionic Equation:
– Anything ionic/ aq, divide into ions. If balancing number for compound is 2, have the balancing
number for both ions as 2 as well.
– Include elements or covalent compounds as they are.
– Any ions that haven’t reacted are spectator ions and get rid of them.
• Acid and Alkali: Ionic equation for neutralisation reaction always H+
(aq) + OH-
(aq) -> H2O (l).
• Acid and Base: Ionic equation is 2H+
(aq) + O2-
(s) -> H2O (l). Remember to have all state symbols
as (aq).
• Acid and Metal Carbonate: H2SO4 (aq) + Na2CO3 (aq) -> Na2SO4 (s) + CO2 (g) + H2O (l). 2Na+ and
CO3
2- are the ions.
• Acid and Metal: 2HNO3 + Mg (s) -> Mg(NO3)2 (aq) + H2. Mg2+ and NO3
– are the ions.