What is the relative formula mass of 2Cu(NO3)2?
I could do it if it was just Cu(NO3)2 but I don't know how you deal with the brackets when there is also a big number in front?
2 answers
The formula mass is the same. When you calculate Cu + 2N + 6O that gives the formula mass of 1 mol Cu(NO3)2. If a 2 is in front, that means TWO mols Cu(NO3)2 so you have twice that amount but the formula mass hasn't changed. 3Cu(NO3)2 is three times that amount but the formula mass is the same.
Many thanks :)