Roundup, an herbicide manufactured by Monsanto, has the formula C3H8NO5P. How many moles of molecules are there in a 669.1-g sample of Roundup?

2.4 * 10^24 molecules of the herbicide.

Explanation:

We must first obtain the molar mass of the compound as follows;

C3H8NO5P = [3 (12) + 8 (1) + 14 + 5 (16) + 31] = [36 + 8 + 14 + 80 + 31] = 169 gmol-1

We know that one mole of a compound contains the Avogadro's number of molecules.

Hence;

169 g of the herbicide contains 6.02*10^23 molecules

Therefore 669.1 g of the herbicide contains 669.1 * 6.02*10^23 / 169 = 2.4 * 10^24 molecules of the herbicide.