Coal is not a pure chemical compound, but its elemental composition can be approximated by the formula C135H96NO9S. What is the approximate percentage by mass of sulfur in coal?
Answers
FeCr2O4 molar mass 223.847 g/mol Find %O in FeCr2O4.
%O = [4(15.9994 g)/(223.847 g)] x 100% = 28.59% O
5. 29%
C135H96NO9S molar mass 1908.272 g/mol Find % S in C135H96NO9S
%S = [(32.064 g)/(1908.272 g)] x 100% = 1.6802 % S
3. 1.68%
Mass Ni = 100 g sample x 18% = 100 g(0.18) = 18 g Ni 2. 18. grams
Note: The atomic mass of Ni is totally unnecessary.
C2H5COOH = C3H6O2 molar mass = 74.0785 g/mol
%C = [(36.0321 g)/(74.0785 g)] x 100% = 48.64%
%H = [(6.0476 g)/(74.0785 g)] x 100% = 8.164%
Answer: 5. 48.63% C, 8.18% H, 43.19% O
26.56% K; 35.41% Cr; 38.00% O. Assume that the sample size is 100 g and each of the percentages given are in units of grams.
26.56 g K; 35.41 g Cr; 38.00 g O Now, calculate the number of moles of each element.
moles K = (26.56 g)/(39.0983 g) = 0.6793 mol = .68 mol
moles Cr = (35.41)/(51.996 g) = 0.6810 mol = .68 mol
moles O = (38.00 g)/(15.9994 g) = 2.375 mol = 2.38 mol
Now, divide each number of moles by the smallest number to get the relative numbers of each atom in the formula. This will be the empirical formula.
K = .68/.68 = 1.0; Cr = .68/.68 = 1.0; O = 2.38/.68 = 3.5 Since we need to have whole numbers, the empirical formula will be K2Cr2O7.