Rules leading to correct formula Please copy into your exercise books 1. Positive ions (cations) can join to negative ions (anions) 2. Positive ions usually form the first part of the name (99% cases) 3. If the formula is correct there is no overall charge 4. If you have more than one polyatomic ion it is placed inside brackets
Essential training ions Positive ions (Cations) Negative ions (Anions) + 1 - 1 +2 - 2 +3 - 3 sodium Na potassium K hydrogen H lithium Li silver Ag fluoride F chloride Cl bromide Br hydroxide OH nitrate NO3 nitrite NO2 hydrogencarbonate HCO3 magnesium Mg calcium Ca barium Ba zinc Zn iron(11) Fe copper Cu carbonate CO3 oxide O sulphide S sulphate SO4 sulphite SO3 chromate CrO4 aluminium Al chromium Cr iron(111) Fe nitride N phosphate PO4 ammonium NH4
NaF NaBr NaNO3 NaHCO3 The easy way to learn these!
NH4F NH4Cl NH4OH (NH4)2CO3 (NH4)2S N.B. all numbers should be lowercase and subscript
Repeat this process linking each positive to each negative ion
Chemical Formulae CHARGES IONS NUMBERS FORMULA calcium hydrogencarbonate Ca HCO3
Chemical Formulae CHARGES IONS NUMBERS FORMULA lead(11) phosphate Pb PO4
Chemical Formulae CHARGES IONS NUMBERS FORMULA ammonium dichromate NH4 Cr2O7
In chemistry there are millions of chemical reactions. But most reactions can be classified as one of four types of reactions: Synthesis: A + B -> AB Decomposition: AB -> A + B Single Replacement: A + BC -> AC + B Double Replacement: AB + CD -> AD + CB
Synthesis (Composition) In a synthesis reaction (also known as a composition reaction), two substances combine to form a larger substance. C OO + C OO
Here are 3 synthesis reactions: Hydrogen + oxygen yields water 2H 2 + O 2 -> 2H 2 O Magnesium + nitrogen yields magnesium nitride 3Mg + N 2 -> Mg 3 N 2 Iron + sulphur yields iron(II) sulphide Fe + S -> FeS
3H2 + N2 -------> 2NH3 4Na + 02 -------> 2Na2O H2 + Cl2 --------> 2HCl Write balanced chemical equations for the following synthesis reactions hydrogen + chlorine --------> hydrogen chloride sodium + oxygen -----------> sodium oxide nitrogen + hydrogen --------------> ammonia ANSWERS UNDER HERE Mr G
Decomposition In a decomposition reaction, a larger substance breaks apart and forms two or more simpler substances.
The first thing you may notice about a decomposition reaction is that it is the complete opposite of a synthesis reaction. In fact many synthesis reactions can be reversed into a decomposition reaction. When you burn hydrogen gas, the hydrogen combines with oxygen to produce water. 2H 2 + O 2 -> 2H 2 O With an electrical current, water can be decomposed into hydrogen and oxygen gas. 2H 2 O -> 2H 2 + O 2
Some examples of decomposition Heat copper carbonate and it will decompose (Refer to flash animation.swf) CuCO 3 -> CuO + CO 2 (Most carbonates decompose producing the oxide and carbon dioxide) Heat lead(11) hydroxide and it will decompose Pb(OH) 2 -> PbO + H 2 O
Solutions Cu(OH)2 ------> CuO + H20 2NaNO3 ------> 2NaNO2 + 02 2Hg2O --------> 4Hg + O2 2Zn(N03)2 ------->2ZnO +4NO2 + O2 CaCO3 --------> CaO + CO2 QUESTION SOLUTIONS UNDER HERE
Single Replacement In a single replacement reaction, a more active element replaces a less active element in a compound. more reactive less reactive
Single Replacement Here Mg is more reactive than Pb
Single Replacement No surprise! fluorine is more reactive than chlorine If fluorine gas is bubbled through a solution of potassium chloride, the fluorine will replace the chlorine. 2KCl + F --> 2KF + Cl This reaction can be represented as follows;
A double replacement change Na Br Mg O H O H Na Br Look at arrows how do they rearrange? + What is reacting with what?
Double Replacements Na Br Mg O H O H Na Br Products from previous page +
The whole chemical reaction NaNa Br Mg O H O H NaNa Br Mg(OH)2 + 2NaBr --> MgBr2 + 2NaOH + Mg Br NaNa NaNa OO H H + + Notice the atoms or ions are just rearranged The number of atoms on both sides of arrow are the same
Now write equations for the following double replacement reactions silver nitrate + sodium chloride ? nitrate + ? chloride copper sulphate + sodium ? copper hydroxide ? nitrate + ? = unknown part lead iodide potassium nitrate + ? ? +