Chapter 10 NOTES PRACTICE PROBLEMS

Try 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? Known Mass of Mg = 9.03g Mass of N = 3.48 g Total mass of cmpd. = 12.51 g (9.03g + 3.48g) Unknown % Mg = ? % N = ?

Solve % Mg = 9.03 g x 100% = 72% 12.51 g % N = 3.48 g x 100% = 28%

Try 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? Known Mass of cmpd = 14.2g Mass of Hg = 13.2 g Mass of O = 1.0 g (14.2g – 13.2g) Unknown % Hg = ? % O = ?

Solve % Hg = 13.2g x 100% = 93% 14.2g % O = 1.0g x 100% = 7%

Try it on your own! Calculate the percent composition of ethane (C2H6). Know: mass of C in 1 mol ethane= 2X12=24g Mass of H in 1 mol ethane=1X6=6g Unknown: Percent C? Percent H? Molar mass= 24g+6g= 30g

Solve %C= 24g X 100 = 80% 30g %H= 6g X 100= 20% % equals 100!

Try it on your own Calculate the percent nitrogen in NH₄NO₃ Know: mass of N in 1 mol NH₄NO₃= 14X2=28g Know: molar mass NH₄NO₃= (14X2)+(4X1)+(3X16)= 28g Unknown: percent N?

Solve % N = 28g X 100 = 35% 80g This is correct because: %H= 4g X100 = 5% %O = 48g X 100= 60%