When 12.35g of cuco3 is heated mass of cuo obtained?

Answer 1

One must always first have the correct, balanced, chemical equation in order to answer general chemistry questions like this one. Once the student can answer a question such as this one, he can answer any questions since they all require the same information. The only difference in the questions is that for one question the student may need to convert grams to moles first, and for other questions the student may need to convert moles to grams first. Since the number of moles of any element or compound is directly proportional to the number of atoms or molecules, virtually any question that involves a chemical equation will ultimately require the number of moles, not grams, of each reactant and/or product.

Now, let's solve this very simple question:

The chemical equation must be CuCO3 ---> CO2 + CuO, and it tells us that for each mole of CuO formed, one mole of CuCO3 is consumed, therefore if we know the no. of moles of CuCO3 that reacted, then the same number of moles of CuO was formed. (I am assuming that the reaction goes to completion, that is all of the cupric carbonate reacts.) Thus, all that is needed to answer the question is to: 1) determine the number of moles of CuCO3 that reacted, and 2) calculate the number of grams of CuO that number of moles of CuCO3 would generate according to the chemical equation.

The formula wt. of CuCO3 is: 63.546 + 12.011 + (3)(15.999) = 123.55 g/mol. Thus, 12.35 g of CuCO3 = 12.35 g CuCO3/123.55 g CuCO3/mol CuCO3 = 0.1000 mol CuCO3.

Again, per the chemical equation, one CuO species is generated for each CuCO3 that disproportionates, therefore 0.1000 mol of CuO is created from 0.1000 mol of CuCO3. The molecular wt. of CuO is 63.546 + 15.999 = 79.545 g/mol, hence 0.1000 mol of CuO has a mass of 79.545 g/mol x 0.1000 mol = 7.954 g CuO.