CHEMISTRY!! The percent composition--Given. Chemical formula-- Find.

Question

The percent composition of a common product in industry and present in kichen is 27.37% Na, 120% H, 14,3% C and 57,14% O.Its plain formula and molecular formula is the same. Determine its chemical formula.

Answer 1

In this problem we need to determine the mole ratio of elements in order to determine its empirical formula.  First, we need to use the percent compositions to determine the number of moles for each element.  Assume you have a 100g sample and the percent value is equal to its numerical mass.  Covering the percentages to grams gives us 27.37g Na, 14.3g C, ...etc (Just for clarity the %H in the problem should be written as 1.2%)  Using the molar mass for each element convert grams to moles: 1.19 mol Na, 1.19mol H, 1.19 mol C, and 3.57mol O.  Now divide each mole number by the smallest number of moles obtained.  For example, 1.19 mole Na/1.19 mole H equals 1.  Therefore, Na and H have a 1:1 mole ratio.  Dividing all the mole ratios by 1.19 yields 1 mole Na, 1 mole H, 1 mole C, and 3 moles O.  Therefore, the empirical formula is NaCHO_3.

It has been indicated in the question that the empirical formula is the same as its molecular formula.  This molecule is named sodium bicarbonate and is commonly found in your kitchen!