If you start with 20.0 grams CaCO3, how many moles of CaCO3 do you have?
mols = g/molar mass. Approximately 0.200 mols.
To calculate the number of moles of CaCO3, you need to divide the given mass (20.0 grams) by the molar mass of CaCO3.
The molar mass of CaCO3 can be determined by adding up the atomic masses of its constituent elements. In this case, Ca has an atomic mass of 40.08 g/mol, C has an atomic mass of 12.01 g/mol, and O has an atomic mass of 16.00 g/mol. So, the molar mass of CaCO3 is:
40.08 g/mol (Ca) + 12.01 g/mol (C) + 3 x 16.00 g/mol (3 O) = 100.09 g/mol
Now, you can use the formula: moles = mass / molar mass.
moles = 20.0 g / 100.09 g/mol = 0.199 moles (approximately 0.200 moles)
Therefore, if you start with 20.0 grams of CaCO3, you have approximately 0.200 moles of CaCO3.