How many oxygen atoms do you have in 2.00 grams of calcium phosphate?

My answer is 3.9*10^22 by multiplying avogadros number by (2/31)

Am I close?

How many Ca^2+ ions do you have in 2.00 grams of calcium phosphate?

I am getting 39, am i close? since there are 3 Ca2+ ions per molecule,I just multiplied that by 13.

2 answers

3,9 x 10^22 is close but not close enough. I used 310.177 for the molar mass. For Ca, multiplying by 13 won't get it. Multiply # moles by 3.
DrWLS gave instructions to you how to solve this problem much much earlier in the day. (But the number of moles is 2/310.177 and not 2/31.)