What is the mass (in grams) of 9.79 × 1024 molecules of methanol (ch3oh)?

We will use this formlula: Mass in grams = Number of moles x Molecular mass of 1 mole.

Since, we know the avagadro number is 6.02 x 10²³, we only have two unknown values left which are the molecular mass of CH3OH and its mole.

Molecular Mass: C = 12, H= 1, O = 16, since we have C=12, H4 = 4, O = 16, we will add them up: 12 + 4 + 16 =32

We know that one mole of anything = 6.02 x 10²³.
So we will use this formula to find the mole of methanol: Number of moles = Number of molecules / Avagadro number

Number of moles of CH3OH = (9.79 x 10^24)/6.02 x 10²³) =  16.263 moles.

Now we know that the molecular mass = 32 and the mole is = 16.263.

Now we can find its mass by using this formula: Mass in grams = Number of moles x Molecular mass of 1 mole.

Mass in grams = 16.263 x 32 = 520g