How many moles of Ca(NO3)2 contain 2.95 x 10^24 oxygen atoms?

Question

I set up the conversions like this:

2.95 x 10^24 / 6.022 x 10^23 to get # of moles Oxygen. Then, I divided that answer by 8, the ratio of oxygen needed to 'make' one unit of calcium nitrite. I get the wrong answer. What am I doing wrong?

Answer 1

each molecule of Ca(NO3)2 contains 6 atoms of oxygen, not 8