A. To calculate the mass of 0.80 mol of Na2CO3, we need to multiply the molar mass of Na2CO3 by the number of moles.
The molar mass of Na2CO3 can be calculated by summing the atomic masses of its constituent elements: Na2CO3 = (2 * Na) + C + (3 * O) = (2 * 23) + 12 + (3 * 16) = 46 + 12 + 48 = 106 g/mol
Now we can calculate the mass: Mass = Number of moles * Molar mass = 0.80 mol * 106 g/mol = 84.8 g
Therefore, the mass of 0.80 mol of Na2CO3 is 84.8 grams.
B. To calculate the amount of substance in 5g of CaCO3, we need to divide the mass by the molar mass of CaCO3.
The molar mass of CaCO3 can be calculated by summing the atomic masses of its constituent elements: CaCO3 = Ca + C + (3 * O) = 40 + 12 + (3 * 16) = 40 + 12 + 48 = 100 g/mol
Now we can calculate the amount of substance: Amount of substance = Mass / Molar mass = 5 g / 100 g/mol = 0.05 mol
Therefore, the amount of substance in 5g of CaCO3 is 0.05 moles.