Balancing Equations To be able to balance equations Tuesday, January 01, 2019 Balancing Equations To be able to balance equations

Symbols Remember, each element has its own symbol(s) - all found in the periodic table Every symbol begins with a capital, and may have one or more other non-capital letters which follow E.g. Oxygen = O Nitrogen = N Sodium = Na Magnesium = Mg Copper = Cu

magnesium + oxygen → magnesium oxide Balancing A chemical reaction can be described by the process reactants → products E.g. magnesium reacts with oxygen, producing magnesium oxide magnesium + oxygen → magnesium oxide 2Mg + O2 → 2MgO

Balancing It is key you know how to balance the equations! Remember: there must always be the same number of atoms on both sides Numbers can only be put in front of the formula when it is needed

magnesium + oxygen → magnesium oxide Look at the following reaction magnesium + oxygen → magnesium oxide 2Mg + O2 → MgO You’ll notice, that there are more green and blue circles on the left hand side, than there are on the right To balance this, we can add a number in front of the right hand side 2Mg + O2 → 2MgO

hydrogen + oxygen → water Look at the following reaction hydrogen + oxygen → water H2 + O2 → H2O Again there is a problem – this time we have an oxygen atom missing from the right hand side To balance this, we can add a number in front of the right hand side H2 + O2 → 2H2O

hydrogen + oxygen → water But this is still unbalanced! hydrogen + oxygen → water H2 + O2 → 2H2O Finally, we can add a number in front of the hydrogen on the left hand side, to balance this up 2H2 + O2 → 2H2O

Example Look at the following reaction: H2SO4 + NaOH → Na2SO4 + H2O The formulas are correct, but the number of atoms on the left are different from those on the right Remember: we can only put numbers in front of the symbols…

Balancing H2SO4 + NaOH → Na2SO4 + H20 In the equation, there are more H atoms on the left, than there are on the right So we can add a 2 in front of the H2O on the right side H2SO4 + NaOH → Na2SO4 + 2H20 Now we have too many H and O atoms on the right hand side, so we can put a 2 in front of the NaOH on the left side H2SO4 + 2NaOH → Na2SO4 + 2H20 Now everything balances! Left hand side = 4 x H; 1 x S; 6 x O; 2 x Na Right hand side = 4 x H; 1 x S; 6 x O; 2 x Na

Questions Write a word equation for what happens when copper burns How many reactants are there in this reaction? What are these reactants? What is the product of the reaction? When you find the mass at the end of the experiment, what chemical are you finding the mass of? Answers copper + oxygen → copper oxide 2 Reactants Reactants: copper + oxygen Product: copper oxide You are calculating the mass of the copper oxide

CaCl2 + AgNO3 → AgCl + Ca(NO3)2 Balance The Equations H2 + O2 → H2O H2 + N2 → NH3 C3H8 + O2 → CO2 + H2O Al + CuO → Al2O3 + Cu K2O + H2O → KOH CaCl2 + AgNO3 → AgCl + Ca(NO3)2

CaCl2 + 2AgNO3 → 2AgCl + Ca(NO3)2 Balance The Equations 2H2 + O2 → 2H2O 3H2 + N2 → 2NH3 C3H8 + 5O2 → 3CO2 + 4H2O 2Al + 3CuO → Al2O3 + 3Cu K2O + H2O → 2KOH CaCl2 + 2AgNO3 → 2AgCl + Ca(NO3)2