Question: how many oxygen atoms are in 0.25 mol of ca(no3)2?
Answer: This means there are half a mole of nitrogen atoms in 0.25 moles of calcium nitrate. This means there are 0.5*6.022*10^23 atoms which equates to 3.011*10^23 atoms. What is the number of moles of oxygen atoms in 3.2 g of CO2?