Balancing Equations TBAT balance chemical equations • What are the symbols • What are the for the following formulas for the elements: following compounds: 1. Sodium 1. Water 2. Oxygen 2. Potassium hydroxide 3. Chlorine 3. Magnesium oxide 4. Iron 4. Potassium iodide 5. Copper 5. Caesium oxide Key facts In chemical reactions new substances are made. A reaction can be summarised in a word equation or a symbol equation. The total mass of reactants is the same as the total mass of products in a reaction A symbol equation must be balanced as no atoms are created or destroyed. State Symbols • (s) • E.g. 1. H2 • (l) 2. O2 • (g) 3. CO2 • (aq) 4. H2O 5. C What is wrong with this equation? • Lithium was added to water in a school lab. Below is the symbol equation for the reaction – or is it? Li(s)+ H2O(s) LiO(aq) + H2(g) http://www.youtube.com/watch?v=8ypUVpwgcAA Balancing equations You can never change a formula when balancing an equation. You can only put a number in front of a formula. Lets consider how to show 2 molecules of CO2: C2O X CO4 X C2O2 X 2CO2 Symbol equations • No atoms are created or destroyed in a chemical reaction. • There should be the same number of atoms of each type of element each side of the equation. – Magnesium + Oxygen Magnesium oxide One carbon atom and two oxygen atoms react. C O O How many atoms are in the product? O C O C + O2 CO2 C O O O C O How Will Our See-Saw Look? C + Cl2 CCl4 Cl Cl C Cl C Cl Cl Cl It’s a Bit Product Heavy C + 2Cl2 CCl4 C Cl Cl C Cl Cl Now everything balances! C + 2Cl2 CCl4 Cl Cl Cl Cl C Cl C Cl Cl Cl How will the see-saw look here? 4O2 + S8 8SO2 S S S S S S S S O O How can we change this? 4O2 + S8 8SO2 S S S S = 8 O = 2 S S S S S O O S = 18 OO== 16 2 O O O O 8O2 + S8 8SO2 S = 8 O O O O O = 16 O O O O O O S S S O O S S S S S S = 8 OO== 16 2 O O 8O2 + S8 8SO2 O O O O O O O O O O S S S O O S S S O O S S S = 8 S = 8 O = 16 O = 16 Balance This Equation Ag + S8 Ag2S Ag = 1 S = 8 Ag = 2 S = 1 Ag Balance these equations 1. C + O2 CO2 2. H2 + O2 H2O 3. N2 + H2 NH3 4. CH4 + O2 CO2 + H2O Balance These Equations Fe + H2SO4 FeSO4 + H2 Mg + HNO3 Mg(NO3)2 + H2 Zn + HCl ZnCl + H2 When you are done turn these into word equations. Question sheet Chemistry What colour is a What colour is an What ions are strong acid on the alkali in made by acids and pH scale? phenolphthalein? alkalis? When you mix an What are the acid and alkali formulas of nitric Define soluble what do you acid and sulphuric and insoluble make? acid? Potassium oxide + Sodium hydroxide Calcium carbonate hydrochloric acid -> + sulphuric acid -> + nitric acid -> Chemistry Chemistry Use the table below to name 3 soluble and 3 insoluble compounds e.g. sodium nitrate lead carbonate Soluble in water Insoluble in water all common sodium, potassium and ammonium salts all nitrates most chlorides silver and lead chloride most sulfates lead, barium and calcium sulfate sodium, potassium and ammonium most carbonates carbonates sodium, potassium and ammonium most hydroxides hydroxides Bingo Make a 3x3 grid with some of these symbols Ag H2 N2 Ar H2O O2 Au H2SO4 -OH CH4 HCl Pt CO2 HNO3 S Cu K Sn Fr Mg Zn.