In an experiment 1.015 g of a metal carbonate, containing an unknown metal M, is heated to give the metal oxide and 0.361 g CO2.
MCO3(s) + heat MO(s) + CO2(g)
What is the identity of the metal M?
mass MO = 1.015 - 0.361 = 0.654 g
moles CO2 = 0.361/44 = ??
moles MO = same as mols CO2.]
moles = grams/molar mass.
You have moles and grams, solve for molar mass of MO, then subtract 16 from that to arrive at the atomic mass M.
To determine the identity of the metal M, we can use the concept of stoichiometry. The molar ratio between the metal carbonate (MCO3) and the CO2 produced can help us determine the molar mass of M and hence its identity.
First, we need to calculate the moles of CO2 produced. To do this, we divide the mass of CO2 by its molar mass:
Molar mass of CO2 (C = 12.01 g/mol; O = 16.00 g/mol):
12.01 g/mol + 16.00 g/mol + 16.00 g/mol = 44.01 g/mol
Moles of CO2 = Mass of CO2 / Molar mass of CO2
Moles of CO2 = 0.361 g / 44.01 g/mol = 0.00821 mol
Using the balanced equation MCO3(s) + heat MO(s) + CO2(g), we can see that the molar ratio between MCO3 and CO2 is 1:1. This means that the number of moles of MCO3 is equal to the number of moles of CO2.
Therefore, the moles of MCO3 = 0.00821 mol.
Next, we calculate the molar mass of MCO3 using its mass and the number of moles:
Molar mass of MCO3 = Mass of MCO3 / Moles of MCO3
Molar mass of MCO3 = 1.015 g / 0.00821 mol = 123.76 g/mol
Now, we know the molar mass of MCO3, and since MCO3 is a metal carbonate, we can assume that the molar mass of M is the atomic mass of M.
From the periodic table, we find the element with a molar mass closest to 123.76 g/mol. In this case, it is sodium (Na), which has a molar mass of approximately 22.99 g/mol.
Therefore, based on the calculated molar mass of MCO3, the metal M is most likely sodium (Na).