4 What is the mass, in grams, of 5.20 x 1023 formula units of NaCl?
A 0.864 grams
11.2 grams
C 50.5 grams
D
304 grams

The mass of NaCl : 50.5 g

The mole is the number of particles(molecules, atoms, ions) contained in a substance  

1 mol = 6.02.10²³ particles

Can be formulated

N=n x No

N = number of particles

n = mol

No = Avogadro's = 6.02.10²³

There are 5.20 x 10²³ units of NaCl, so mol NaCl :

Mass of NaCl(MW=71 g/mol) :

so here we go

atomic mass

239 + 1 = y + 134 + 3 combine like terms

240 = y + 137             subtract 137 from both terms

240 - 137 = y

103 = y

atomic number

94 = z +54 + 0

94 = z + 54               subtract 54 from both sides.

40 = z

answer