Question

1)     What is the mass of water if it contains 5 moles of hydrogen atoms?                              

2)      Aspirin is a compound with the molecular formula C₉H₈O₄. What is its percent composition?

3)     A 24.81-g sample of a gaseous compound containing only carbon, oxygen, and chlorine is determined to contain 3.01 g C, 4.00 g O, and 17.81 g Cl. What is this compound’s percent composition?

Answer 1

1) Molar mass of water = 18.0g

Mass$= \frac{5}{2}×18=45g$

2)C= 12×9= 108g

H= 1×8=8g

O=16×4=64g

Total= 180g

C= $\frac{108}{180}×100\%=60\%$

H$= \frac{8}{180}×100\%=4.44\%$

O=$\frac{64}{180}×100\%=35.56\%$

3) $24.81\ne3.01+4.00+17.81$

Taking 3.01 as erroneous and using 3.00 instead

$\frac{3.00}{24.81}×100\%=12.09\%$

$\frac{4.00}{24.81}×100\%=16.12\%$

$\frac{17.81}{24.81}×100\%=71.79\%$