[jacounce]

Here is the question:

1.056g of a metal carbonate, containing an unknown metal M, is heated to give the metal oxide and .376g CO₂.

MCO₃(s) + heat --> MO(s) + CO₂(g)

What is the identity of the metal M?

(a) Ni
(b) Cu
(c) Zn
(d) Ba



Here is what I tried to do.

.376g CO₂ * 1 mol CO₂/44.01g CO₂ * 1mol MCO₃/1 mol CO₂ * 1 mol CO₃/1 mol MCO₃ * 60.01g CO₃/ 1 mol CO₃ = .5127g CO₃

Then:

1.056g MCO₃ - .5127g CO₃ = .5433g M

First of all, is my line of thinking correct up to this point?
Second, what is the next step?

Thanks for any input you can offer.

[opti384]

With my limited time it's difficult to me to check this all - .376g CO2 * 1 mol CO2/44.01g CO2 * 1mol MCO3/1 mol CO2 * 1 mol CO3/1 mol MCO3 * 60.01g CO3/ 1 mol CO3 = .5127g CO3.

So I'll give you a hint instead.

1.056g will equal to sum of the mass of MO and CO_2.

Also as you can see in the reaction same mols of CO2 and MO are produced.

[jacounce]

Well, thank you for that hint but I know that matter is not created or destroyed already.

I still don't understand how to identify the unknown metal from the discovered weight in grams.

[Borek]

You need to find out number of moles and molar mass.

0.5127g is OK.

[Invincible]

Look at the mole to mole ratio.  CO2 is 44.01g/mole
Oxygen is ~16g
unknown is 16+n g

1.056g = n-0.376g

You can look up that CO2 is 44.01g/mol

Convert the mass of whatever is left behind to moles and you'll get
n is 79.6g/mol and its already given that its got one oxygen atom, so subtract that.  Then look it up in periodic table.