How many particles are in 50.0 grams of each of the following? NaHCO3?

Question

How many particles are in 50.0 grams of each of the following?

1. NaHCO3

2. NaCl

3. Al2(SO4)3

Answer 1

If given a gram mass, then the general formula for conversion is

(grams) (moles / gram) (molecules / mole) = molecules

The 1st term of the product you already have: 50 g

The 2nd term is the inverse of the molecular or formula weight.

The 3rd term is Avogadro's number.  Note that a "particle" for a chemical compound is synonymous for "molecule."

Notice how all the dimensions cancel out in numerator-denominator fashion to give you the answer.  That is how virtually every conversion calculation can be done...just by setting up dimensions so that they cancel in a way to give you the final desired dimension.

Now you just execute.  First gather your necessary data:

FW of NaCl = 58.44 g/mol

FW of NaHCO3 = 84.01 g/mol

FW of Al2(SO4)3 = 342.15 g/mol

Avogadro's Number = 6.023e23 molecules / mol

Now run through the calculations (note the significant figures or digits!)

NaHCO3: (50.0 g)(1 mol/84.01 g)(6.023e23 molecules/mol) = 3.58e23

NaCl:  (50.0 g)(1 mol/58.44 g)(6.023e23 molecules/mol) = 5.15e23

Al2(SO4)3:  (50.0)(1/342.15)(6.023e23) = 8.80e22