How many formula units of #CuCl_2# are present in a #12.53*g# mass of the salt?

1 Answer
anor277
Feb 15, 2018

Well what is the formula mass of cupric chloride....?

Explanation:

The anhydrous salt has a formula mass of #134.45* g*mol^-1 #. How did I get this?

And so we take the QUOTIENT....#"mass"/"formula mass"#...

...#(12.53*cancelg)/(134.45* cancelg*mol^-1)=0.0932*mol#

And so how does this molar quantity help us? Well we know that BY DEFINITION one mole specifies #"Avogadro's number"# of formula units....where .........

#N_A-="Avocado number"=6.022xx10^23*mol^-1#

And so we take the product...

#"molar quantity"xx"Avogadro's number"#

#0.0932*molxx6.022xx10^23*mol^-1-=5.62xx10^22*"formula units"#

...and we are careful to speak of #"formula units"# of #CuCl_2#. How many copper atoms, and how many chlorine atoms are in this quantity?

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