how do i calculate the empirical formula for compounds with the following compositions?

Question

a. Fe: 63.5%, S: 36.5%
b. Mn: 63.1%, S: 36.9%
c. K: 26.6%, Cr: 35.4%, O: 38.0%

thanks

Answer 1

a.) Assume 100 g of compound..
amount of Fe = 0.635 x 100g = 63.5g
amount of S = 0.365 x 100g = 36.5g
mole Fe = 63.5g / 55.845 = 1.137
mole S = 36.5 g / 32.065 = 1.138

molecular formula = mole Fe / mole S = 1.137 / 1.138 = 1
1 is to 1 ratio
thus, FeS

b.) Assume 100 g of compound..
amount of Mn = 0.631 x 100g = 63.1g
amount of S = 0.369 x 100g = 36.9g
mole Mn = 63.1g / 54.938 = 1.149
mole S = 36.9 g / 32.065 = 1.151

molecular formula = mole Mn / mole S = 1.149 / 1.151 = 1
1 is to 1 ratio
thus, MnS

c.) Assume 100 g of compound..
amount of K = 0.266 x 100g = 26.6g
amount of Cr = 0.354 x 100g = 35.4g
amount of O = 0.380 x 100g = 38.0g
mole K = 26.6 g / 39.098 = 0.680
mole Cr = 35.4 g / 51.996 = 0.680
mole O = 38.0 g / 16.00 = 2.375


molecular formula = mole O / mole K = 2.375 / 0.680 = 3.5
2 is to 7 ratio
thus, K2Cr2O7

Answer 2

Tom is right in his approach yet he provides a pair of pointless steps. you in uncomplicated terms prefer evaluate atomic O and atomic S (no longer the compounds), so which you may desire to make certain the variety of moles you like in uncomplicated terms divide via the atomic weight (sixteen for O and 32 for S) and not the molecular weights. once you're taking the mole ratio, you will locate that there are a million.5 O for each a million S and you relatively get the S2O3 empirical formulation. you won't be able to get the molecular formulation from this venture (and there is not any could desire to apply the molecular sorts of O and S in his very final step). the respond is S2O3

Answer 3

pretend the percentages are grams:
63.5 grams Fe, 36.5 grams S.
Then convert to moles: 55.845 grams per mole for iron, so 63.5 grams divided by that gives 1.14 moles Fe. do the same for S: 36.5 grams divided by 32.065 which also happens to equal 1.14. since the moles are a one-to one ratio, the empirical formula is FeS. For others, if the ratios are different, divide each of the other moles by the smallest number to get the molecular ratios. Repeat the steps for the others, and you'll do fine.

Answer 4

Change % to grams then to moles

then divide the larger number by the smaller one

Answer 5

a. 0.635W = 55.85n
0.365W = 32.07m
55.85n/0.635 = 32.07m/0.365
n/m = 0.99898 ≈ 1
so you have FeS

Another approach:

(b)
54.94n / (54.94n + 32.07m) = 0.631
32.07m / (54.94n + 32.07m) = 0.369
54.94n = 0.631(54.94n + 32.07m)
54.94n = 34.66714n + 20.23617m
20.27286n = 20.23617m
MnS

Answer 6

screw chemistry!!!