PERCENT COMPOSITION• Percent composition is used to find the

percentage of elements in a compound. One must know the molar mass of the elements and the compound in order to get percent composition. For instance, the percent composition of oxygen in water is 89%. The molar mass of water is 18g/mol, and oxygen has a molar mass of 16g/mol. 16 divided by 18 is .89. Multiply this by 100 and you get 89%. This leaves hydrogen making up 11% of the water compound.

Question #2 The percent by mass of iodine in KI is approximately[A] 77%[B] 50%[C] 80%[D] 36%

Question #3 The percent by mass of chlorine in SCl4 is approximately[A] 62%[B] 98%[C] 81%[D] 25%

Question #4What is the percent by mass of calcium in CaSO4.2H20?[A] 32%[B] 23%[C] 51%[D] 84%

Question #5What is the percent by mass of iron in Iron (III) oxide?[A] 60%[B] 40%[C] 30%[D] 70%

Question #6 What is the gram formula mass of sodium hydrogen carbonate?[A] 100g[B] 48g[C] 84g[D] 95g

Question #7 What is the percent by mass of rubidium in Rb2O?[A] 70%[B] 99%[C] 43%[D] 91%

Question #8 The percent composition by mass of each element in a compound[A] can be calculated scientifically[B] can not be calculated[C] can be calculated mathematically[D] is a fact

Question #9What is the percent by mass of Boron in BF3?[A] 10%[B] 20%[C] 18%[D] 16%

Question #10 What is the percent by mass of sodium in Na2O?[A] 72%[B] 74%[C] 76%