how many molecules are in 75.8 g of NaCl?

Answer 1

Maybe a trick question, maybe not.

There are actually NO molecules in 75.8 g of NaCl. There are formula units, but not molecules.

Answer 2

First determine how many moles that is by dividing 75.8 grams by the molar mass. To figure out what the molar mass is, use the periodic table:

Na: 22.990 g/mol x 1 atom = 22.990 g/mol

Cl: 35.453 g/mol x 1 atom = 35.453 g/mol

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Molar Mass for NaCl: 58.443 g/mol

(75.8 g)/(58.443 g/mol) = 1.297 moles

Then use Avogadro's Number to calculate how many molecules there are: (1.297 moles)(6.022 x 1023 molecules/mole) = 7.81 x 10²³ molecules