Question

1. You started with 1.000 g of a unknown and isolated 0.9550g of metallic Cu. What is the calculated formula weigth of your compound? is this reasonable? If so, why? If, not what happened to give you this result (give details of potential contributing errors)?

Answer 1

solution:

first, calculate the number of mole of 0.9550g Cu:

moles of Cu = 0.9550 g / 63.55 = 0.01503 mol Cu

To form 0.01503 mole of Cu, unknow compound should have either

0.01503 mol Cu or 2 * (0.01503 mol Cu) or 3 * (0.01503 mol Cu)

Then, the formula weight of compound is either

1.000 g / 0.01503 mol Cu = 66.53 g / mol

(or) 1.000 g / (2 * 0.01503 mol Cu) = 33.267 g/mol

(or) 1.000 g / (3 * 0.01503 mol Cu) = 22.178 g/mol

the above values are not reasonable, as they should have formula mass much more than 63.55 g/ml. this can be due t reasons like incomplete solubility of compound, error in mass measurements etc.