How many oxygen atoms would it produce if it is completely decomposed?
Consider a sample of calcium carbonate in the form of a cube measuring 1.25 in on each edge. If the sample has a density of 2.71 g/cm3, how many oxygen atoms would it produce if it is completely decomposed?
Calcium carbonate is CaCO3. If heated to around 800 degrees C, it thermally decomposes to CaO and CO2. The equation is written below:
CaCO3 --> CaO + CO2
If by "how many oxygen atoms would it produce" you mean how many oxygen atoms would be liberated as a part of CO2, there there will be 2 atoms of O produced per molecule of CaCO3 burned. So we need to figure out the moles of CaCO3 in the solid sample. The cube has a side length of 1.25 inches. Since there are 2.54 cm per inch, this gives:
1.25 in (2.54 cm/1 in) = 3.175 cm
To find the volume of the cube, simply cube the length of one side:
(3.175 cm)^3 = 32.006 cm^3
Multiply the volume by the density to get the mass of the sample in grams:
32.006 cm^3 (2.71 g/cm^3) = 86.74 g CaCO3
Now divide by the molecular weight of CaCO3 to get the moles:
86.74 g (1 mole/100.09 g) = 0.867 moles CaCO3
Every mole of CaCO3 gives one mole of CO2 which contains 2 moles of oxygen for a total of 0.867*2 = 1.734 moles O. Now multiply by Avogadro's number to get the total number of atoms of oxygen:
1.734 moles O (6.022 x 10^23 atoms/1 mole) = 1.04 x 10^24 atoms O.
So a total of 1.04 x 10^24 oxygen atoms would be produced.
If by totally decomposed you mean that all three atoms of oxygen are somehow released, then multiply the moles of CaCO3 times 3 and then multiply by Avogadro's number:
2.601 moles O (6.022 x 10^23 atoms/1 mole) = 1.57 x 10^24 atoms O.