Question

% (by mass) sulfur? What is the formula of the compound between calcium and sulfur that has the percent composition 55.6% (by mass) calcium and 44.4% (by mass) sulfur? Ca2S4 CaS Ca2S CaS4 CaS2 Request

Answer 1

Answer: The empirical formula is $CaS$

Explanation:

If percentage are given then we are taking total mass is 100 grams.

So, the mass of each element is equal to the percentage given.

Mass of Ca= 55.6 g

Mass of S = 44.4 g  

Step 1 : convert given masses into moles.

Moles of Ca =$\frac{\text{ given mass of Ca}}{\text{ molar mass of Ca}}= \frac{55.6g}{40.08g/mole}=1.38moles$

Moles of S =$\frac{\text{ given mass of S}}{\text{ molar mass of S}}= \frac{44.4g}{32.06g/mole}=1.38moles$

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For Ca = $\frac{1.38}{1.38}=1$

For S = $\frac{1.38}{1.38}=1$  

The ratio of Ca : S =  1:1  

Hence the empirical formula is $CaS$