To calculate the number of molecules ch3cooh in a given amount of vinegar, we first need to determine the amount of ch3cooh in the solution by multiplying the percent ch3cooh with the sample amount. Then, convert g to moles and use avogadro's number. We do as follows:
41.9 g vinegar solution ( .05 g ch3cooh / g vinegar solution ) (1 mol / 60.05 g ) ( 6.022x10^23 g / 1 mol ) = 2.1x10^22 molecules ch3cooh