How many molecules of benzene (C6H6) are in 17.4 g of benzene?

(Show ALL work and answer with correct significant figures and units.)

1.34×10²³ molecules of C₆H₆

Explanation:

Firs ot all we need to the determine the amount of benzene, in 17.4 grams of it.

Molar mass from benzene = 78 g/mol

Let's convert the grams to mol → 17.4 g . 1mol / 78 g = 0.223 moles

We know, that 1 mol of anything contains the Avogadro's Number, 6.02×10²³ particles. Let's count the molecules

1 mol of benzene has NA molecules

Therefore 0.223 moles must have (0.223 . 6.02×10²³) / 1 = 1.34×10²³ molecules of benzene

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%