Title CHE JR ST M 05 MASS OF ELE(26 May 2016).ppt ✅

STOICHIOMETRY
% MASS OF AN ELEMENT
Percentage composition and molecular formula… Example : Formula mass of Fe3O4 = 232 % of Fe 3 × 56 × 100 232 = % of ‘O’ 4 × 16 × 100 232 = = 27.5% = 72.5% % mass of an element No of atoms × atomic mass of element × 100 Formula mass of substance =
2. Calculate the mass percent of different elements present in ethyl alcohol (C2H5 OH). Solution : Molar mass of ethanol = 2 x 12.01+6 x 1.008 +16.00 = 46.068 g Mass % of carbon Mass % of hydrogen Mass % of carbon 24.02 46.068 = × 100 = 52.14% 6.048 46.068 = × 100 = 13.13% 16.00 46.068 = × 100 = 34.73%