To calculate the number of atoms of Cr, we first find the number of moles per unit of cubic centimeter of Cr. Then, use avogadros number for the number of atoms. Calculations are as follows:
1 cm^3 (7.15 g/cm^3) (1 mol / 51.996 g Cr) = 0.14 mol Cr
0.14 mol Cr ( 6.022 x 10^23 atoms Cr / 1 mol Cr ) = 8.28 x 10^22 atoms Cr
Answer: C2HNO3
Explanation: C = 27.59/12.011 = 2.297
H = 1.15/1.008 = 1.1409
N = 16.09/14.007 = 1.1487
O = 55.17/15.999 = 3.4483
Divide by smallest result:
C = 2
H=1
N=1
O = 3
Empirical formula = C2HNO3
Third choice because the others make no sense
