Agnes Pockels (1862-1935) was able to determine Avogadro's number using only a few household chemicals, in particular oleic acid, whose formula is C18H34O2.
(a) What is the molar mass of this acid?
(b) The mass of one drop of oleic acid is 2.3 × 10−5 g and the volume is 2.6 × 10−5 cm 3 . How many moles of oleic acid are there in one drop?
(c) Now all Pockels needed was to find the number of molecules of oleic acid. Luckily, when oleic acid is spread out on water, it lines up in a layer one molecule thick. If the base of the molecule of oleic acid is a square of side d, the height of the molecule is known to be 7 d. Pockels spread out one drop of oleic acid on some water, and measured the area to be 70.0 cm2. Using the volume and the area of oleic acid, what is d?
(d) If we assume that this film is one molecule thick, how many molecules of oleic acid are there in the drop?
(e) What value does this give you for Avogadro's number?