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Balancing Equations LI: To be able to balance simple equations
08/11/2019 Balancing Equations LI: To be able to balance simple equations SC: Convert a word equation into a symbol equation Balance an equation
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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. The conservation of mass in a chemical reaction is an essential prerequisite to understanding why we need to balance equations.
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Small numbers The small numbers we sometimes see are called subscripts. O2 This subscript number means there are two oxygen atoms O O
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Big numbers The big numbers we sometimes see are called coefficients
This coefficient number means there are two lots of the oxygen molecules O O O O
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One carbon atom and two oxygen atoms react
One carbon atom and two oxygen atoms react. How many atoms are in the product? C O O C
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C + O2 CO2 C O O C
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How Will Our See-Saw Look?
C + Cl2 CCl4 Cl C C Cl
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It’s a Bit Product Heavy
C + 2Cl2 CCl4 Cl C Cl C Cl
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Now everything balances!
C + 2Cl2 CCl4 Cl C Cl C Cl
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How will the see-saw look here?
4O2 + S8 8SO2 S O S O
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4O2 + S8 8SO2 How can we change this? O S O S O S O S O S O S O S
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8O2 + S8 8SO2 O O S = 8 O = 16 O O O O O S O S O O S O S O O S O S O
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8O2 + S8 8SO2 O O O S O O S O S O O O S O O S O O S O S O O S S = 8
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Ag + S8 Ag2S Balance This Equation Ag Ag = 1 S = 8 Ag = 2 S = 1 Ag S
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Balance These Equations
Fe + H2SO4 FeSO4 + H2 Mg + HNO3 Mg(NO3)2 + H2 Zn + HCl ZnCl + H2 Extension: When you are done turn these into word equations.
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