Asteroid wrote:how do you guys do this. i got chem hnrs and maybe ap next year and didnt get that at all
Step1: Making sure your molecules have the correct composition.
EG If you place a single charged kation (+charge) with double negative anion (-charge) you should realise that you need 2kations to balance the molecule.
EG:
Sodium: Na. It'll become Na+
Oxygen: O > O2-.
Thus sodiumoxide will be Na2O.
1st line: +1
2nd line: +2
3rd line: +3
5th line: -3
6th line: -2
7th line: -1
the others need to be learned by hearth because it's slight more complicated.
EG Iron: Fe can be Fe2+ or Fe 3+.
Step 2: writing the equation down.
Sodium carbonate + hydrochloric acid --------> sodium chloride + water + carbon dioxide
That gives:
Na2CO3 + HCl => NaCl + H2O + CO2
Step 3: Puzzling with the help of a pencil.
You see 2 sodium left and 1 right. Thus you write a 2 in front of NaCl.
Thus you'll see 2 chlorides right, leading to a adding a 2 in front of HCl.
This gives 2 hydrogens left and you see 2 on the right.
And because there are 3oxygens and 1 crabon left and right, you know that the equation fits.
This works for all substitution and acid/base reactions.
Reactions involving oxidations and reductions are solved somewhat different but I'm sure they'll explain that later.