Equations and Acids

Ionic Compounds

• A ionic compound is a compound formed by ions onding together through electrostatic forces.
• Metal ions have a positive charge.
• Non-metal ions have a negative charge.

Formula of an ionic compound

• How to work out the formula:
  • Write the formulae of the ions
  • Adjust the number of each ion so that there is no overall charge.
• For Example:
  • Magnesium Bromide: - ions are Mg²⁺ and Br^-
  • Need 2 x Br^- to balance Mg²⁺
  • Formula is MgBr_2.

Covalent Compounds

• A molecule formed by covalent bonds, in which the atoms share one or more pairs of electrons.

Ionic Equations

• Ionic equations leave out ions that are unchanged in a reaction.
• The unchanged ions are called spectator ions.

Example

HCl(aq) + NaOH(aq) ---> NaCl(aq) + H₂O(l)

H⁺(aq) + OH^-(aq) ---> H₂O(l)

Acids

• An acid is a proton donor (H⁺ donor)
• Common acis are hydrochloric acid (HCl), sulphuric acid  (H₂SO₄), and nitric acid (HNO₃).
• An acid releases H⁺ ions in aqueous solution.

Bases

• A base is a proton acceptor (H⁺ acceptor).
• Bases are metal oxides, metal hydroxides and ammonia solution.
• Bases destroy acidity in neutralisation reactions.

Alkali

• An alkali is a soluble base.
• Alkalis release OH^- ions in aqueous solution.
• Common alkalis are sodium hydroxide, NaOH, potassium hydroxide, KOH, and aqueous ammonia, NH_3.

Salts

• Salts are produced when the H⁺ an acid is replaced by another positive ion.
• Salts are formed when acids react with bases and carbonates.
• Observations when react:
  • Fizzing 
  • Carbonate dissolves

Example

• Acid + carbonate Ž---> salt + water + carbon dioxide
• 2HCl(aq) + MgCO₃(s) Ž---> MgCl₂(aq) + H₂O(l) + CO₂(g)