How many moles are in CaCl?
The molar mass of CaCl2 is 110.98 g/mol. The conversion factor that can be used is then based on the equality that 1 mol = 110.98 g CaCl2. Dimensional analysis will allow you to calculate the mass of CaCl2 that you should measure. When you measure the mass of 333 g of CaCl2, you are measuring 3.00 moles of CaCl2.
Is O2 2 moles of oxygen?
From here, the answer is simple. Just multiply 2 by 31.9988 g because there are two moles of oxygen.