How might I go about balancing chemical equations?
First let us look at what the specification asks of you as a student:E.g. AQA GCSE chemistry specification 4.3.2.3 Using moles to balance equations (HT only) The balancing numbers in a symbol equation can be calculated from the masses of reactants and products by converting the masses in grams to amounts in moles and converting the numbers of moles to simple whole number ratios. a) Students should be able to balance an equation given the masses of reactants and products. b) Students should be able to change the subject of a mathematical equation. Let’s start with an example question:Balance the following equation: CH4 + Cl2 --> CCl4 + HCl. As soon as you see a question in the exam look for key words: “balance” “equation”. Really use the space you have underneath the question to write down any notes to help you with the question. Underneath balancing equation questions I would suggest using this method: Left hand side: C = 1, H = 4 , Cl = 2 . Right hand side: C=1, H=1, Cl = 5. Initially this looks daunting because of the number of chlorines however, look at the simplest numbers to balance first. In this case this is hydrogen. So first lets try and get the hydrogen to balance by multiplying the HCl on the right hand side by 4. This gives: Left hand side: C = 1, H = 4, Cl = 2. Right hand side: C=1, H=4, Cl=8. Now all you need to do is use simple math to multiply the left hand side Cl2 by 4 to get 8 chlorines on both sides of the equation. This gives a final equation of CH4 + 4Cl2 --> CCl4 + 4HCl. Things to note: 1) You must only change the bigger numbers in front of the chemical compounds (coefficients) and not the smaller numbers inside or after the chemical. 2)Always try to use the lowest ratio of coefficients possible because in my past experience you might get marks deducted.
