q1) the number of moles can be calculated as follows number of moles = mass present / molar mass number of moles is the amount of substance. 4.8 g of Ca was added therefore mass present of Ca is 4.8 g molar mass of Ca is 40 g/mol molar mass is the mass of 1 mol of Ca therefore if we substitute these values in the equation number of moles of Ca = 4.8 g / 40 g/mol = 0.12 mol 0.12 mol of Ca is present
q2) next we are asked to calculate the number of moles of water present again we can use the same equation to find the number of moles of water number of moles = mass present / molar mass 3.6 g of water is present
sum of the products of the molar masses of the individual elements by the number of atoms H - 1 g/mol and O - 16 g/mol molar mass of water = (1 g/mol x 2 ) + 16 g/mol = 18 g/mol molar mass of H₂O is 18 g/mol therefore number of moles of water = 3.6 g / 18 g/mol = 0.2 mol 0.2 mol of water is present
