# chemical equations 1 yr 10 mocks

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• Created by: tia5303
• Created on: 15-07-20 16:38
• chemical equations
• on way to show a chemical reaction is to write a word equation.
• however its not as useful as using chemical symbols because you cant tell straight away what's happened to each of the atoms. It's easy.
• heres an example - methane burns oxygen giving carbon dioxide and water:
• the molecules on the left hand side of the equation are called reactants.
• methane + oxygen ---> carbon dioxide+ water
• the molecules on the right hand side are called the products
• methane + oxygen ---> carbon dioxide+ water
• the molecules on the right hand side are called the products
• symbol equations
• need to be balanced !!!
• there must always be the same number of atoms on both sides of the equation
• you balance the equation by putting numbers in front of the formulas where needed.
• need to be balanced !!!
• there must always be the same number of atoms on both sides of the equation
• you balance the equation by putting numbers in front of the formulas where needed.
• take this equation for reacting sulfuric acid with sodium hydroxide:
• H SO + NaOH -----> Na SO + H O
• the formulas are all correct but the number of atoms don't match up on both sides
• you cant change formulas like H  SO  to H  SO
• you can only put numbers in front of them
• you cant change formulas like H  SO  to H  SO
• you can only put numbers in front of them
• take this equation for reacting sulfuric acid with sodium hydroxide:
• H SO + NaOH -----> Na SO + H O
• the formulas are all correct but the number of atoms don't match up on both sides
• steps to balancing a symbol equation
• 1) find an element that doesn't balance and pencil in a number to try and sort it out.
• 2) see where that gets you. It may create another imbalance, if so, pencil in another number and see where it gets you.
• 3) carry n chasing unbalanced elements and the equation will sort itself out in no time
• example below:
• state symbols tell you the state of a substance in an equation
• symbol equations can also include state symbols next to each substance
• they tell you what physical state the reactants and products are in
• (s) - solid
• (l) - liquid
• (g) - gas
• (aq) - aqueous
• ionic equations show the useful bits of reactions
• in an ionic equation only the reacting particles ( and the products they form) are included
• to write an ionic equation you have to look at the reactants and products.
• anything that's exactly the same on both sides of the equation can be left out.
• example:
• half equations show the movement of electrons
• half equations show how electrons are transferred during reactions.
• e- stands for one electron
• you cant write half equations for all chemical reactions - only the ones where oxidation or reduction happen.
• examples:
• you cant write half equations for all chemical reactions - only the ones where oxidation or reduction happen.
• you can combine half equations to create full ionic equations
• full equations never contain electrons - the electrons in the reactants and products should cancel out
• so in the sodium/hydrogen example (highlighted pink), the full ionic equation would be : 2Na + 2H  --> 2Na  + H