Question #549bf

1 Answer
Oct 24, 2017

3.80*10^23 molecules

Explanation:

To start with, calculate the molar mass of petrol. To do so, we must reference a periodic table with molar masses on it. When we do, we find the molar mass of carbon to be 12.01g and the molar mass of hydrogen to be 1.008g. So (12.01*8)+(1.008*18)=112.224g
We use that to calculate the amount of moles in the sample by dividing the mass of the sample by the calculated molar mass: 72/114.224 to get 0.63 mol of petrol.

Next, we must recall Avogadro's Number which is 6.022*10^23. This represents the amount of molecules per mole. So we multiply this value by the amount of moles in the sample to get the amount of molecules in the sample: 0.63*6.022*10^23=3.8*10^23. Don't forget that the smallest amount of sig figs in the problem is two with 72g so that's how many sig figs should be included in your answer.