2Try it on your own!A compound is formed when 9.03 g Mg combines completely with 3.48 g N. What is the percent composition of this compound?KnownMass of Mg = 9.03gMass of N = 3.48 gTotal mass of cmpd. = g (9.03g g)Unknown% Mg = ?% N = ?
3Solve % Mg = 9.03 g x 100% = 72% 12.51 g % N = 3.48 g x 100% = 28%
4Try it on your own!When a 14.2-g sample of mercury(II) oxide is decomposed into its elements by heating, 13.2 g Hg is obtained. What is the percent composition of the compound?KnownMass of cmpd = 14.2gMass of Hg = 13.2 gMass of O = 1.0 g (14.2g – 13.2g)Unknown% Hg = ?% O = ?
5Solve% Hg = 13.2g x 100% = 93% 14.2g % O = 1.0g x 100% = 7%
6Try it on your own!Calculate the percent composition of ethane (C2H6).Know: mass of C in 1 mol ethane= 2X12=24gMass of H in 1 mol ethane=1X6=6gUnknown: Percent C?Percent H?Molar mass= 24g+6g= 30g
7Solve%C= 24g X 100 = 80%30g%H= 6g X 100= 20%% equals 100!
8Try it on your own Calculate the percent nitrogen in NH₄NO₃ Know: mass of N in 1 mol NH₄NO₃= 14X2=28gKnow: molar mass NH₄NO₃= (14X2)+(4X1)+(3X16)= 28gUnknown: percent N?
9Solve % N = 28g X 100 = 35% 80g This is correct because: %H= 4g X100 = 5%%O = 48g X 100= 60%