Question

During heavy exercise and workout, lactic acid (C₃ H₆ O₃), is produced and accumulates in muscles where it can cause pain and soreness ("burn"), especially un anaerobic (absence of oxygen) conditions. (a) How many molecules of lactic acid are there in 0.754 moles of lactic acid? (b) How many atoms of carbon (C) are there in 2.33 moles of lactic acid? (c) How many moles of lactic acid will contain 3.77 x 10²¹ atoms of oxygen (O)?

Answer 1

a)

use:

number of molecules = number of mol * Avogadro’s number

number of molecules = 0.754 * 6.022*10^23 molecules

number of molecules = 4.541*10^23 molecules

Answer: 4.54*10^23 molecules

b)

use:

number of molecules = number of mol * Avogadro’s number

number of molecules = 2.33 * 6.022*10^23 molecules

number of molecules = 1.403*10^24 molecules

1 molecule of C3H6O3 has 3 atoms of C

So,

number of C= 3*number of molecules

= 3*1.403*10^24

= 4.21*10^24 atoms

Answer: 4.21*10^24 atoms

c)

1 molecule of C3H6O3 has 3 atoms of O

so,

number of molecules = number of atoms / 3

= (3.77*10^21)/3

= 1.26*10^21 moelcules

use:

number of mol = number of molecules / Avogadro’s number

number of mol = 1.26*10^21 / 6.022*10^23 mol

number of mol = 2.092*10^-3 mol

Answer: 2.09*10^-3 mol