Equations - Formulae (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 MgBr2.
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Equations - Formulae (Covalent Compounds)
- A molecule formed by covalent bonds, in which the atoms share one or more pairs of electrons.
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- Ionic equations leave out ions that are unchanged in a reaction.
- The unchanged ions are called spectator ions.
HCl(aq) + NaOH(aq) ---> NaCl(aq) + H2O(l)
H+(aq) + OH-(aq) ---> H2O(l)
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- 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.
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- A base is a proton acceptor (H+ acceptor).
- Bases are metal oxides, metal hydroxides and ammonia solution.
- Bases destroy acidity in neutralisation reactions.
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- 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, NH3.
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- 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:
- Carbonate dissolves
- Acid + carbonate ---> salt + water + carbon dioxide
- 2HCl(aq) + MgCO3(s) ---> MgCl2(aq) + H2O(l) + CO2(g)
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