Question 6.4: Lactic acid, the substance that builds up in muscles and cau......
Lactic acid, the substance that builds up in muscles and causes them to hurt when they are worked hard, has the formula C_{3}H_{6}O_{3}. How many moles of carbon atoms, hydrogen atoms, and oxygen atoms are present in a 1.2-mole sample of lactic acid?
One mole of C_{3}H_{6}O_{3} contains 3 moles of carbon atoms, 6 moles of hydrogen atoms, and 3 moles of oxygen atoms. We obtain the following conversion factors from this statement:
\quad\quad (\frac{3 moles C atoms}{1 mole C_{3}H_{6}O_{3}})(\frac{6 moles H atoms}{1 mole C_{3}H_{6}O_{3}})(\frac{3 moles O atoms }{1 mole C_{3}H_{6}O_{3}})
Using the first conversion factor, we calculate the moles of carbon atoms present as follows:
\quad\quad\quad\quad 1.2 \cancel{moles C_{3}H_{6}O_{3}}\times (\frac{3 moles C atoms}{1 \cancel{mole C_{3}H_{6}O_{3}}})=3.6 moles C atoms
Similarly, from the second and third conversion factors, the moles of hydrogen and oxygen atoms present are calculated as follows:
\quad\quad\quad\quad 1.2 \cancel{moles C_{3}H_{6}O_{3}}\times (\frac{6 moles H atoms}{1 \cancel{mole C_{3}H_{6}O_{3}}})=7.2 moles H atoms
\quad\quad\quad\quad 1.2 \cancel{moles C_{3}H_{6}O_{3}}\times (\frac{3 moles O atoms}{1 \cancel{mole C_{3}H_{6}O_{3}}})=3.6 moles O atoms