How many formula units are present in a #12.6*g# mass of #MgCl_2#?

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Answer 1 · 2017-06-17T17:01:52

Approx. #8xx10^22# #"formula units............"#

We find the molar quantity by dividing the mass of substance by the molar mass.....

#(12.6*g)/(95.21*g*mol^-1)=0.132*mol#

How did I get the #95.21*g*mol^-1# number?

And this there are #0.132*mol# #Mg#, and #2xx0.132# #Cl# atoms....

But a mole is SIMPLY A NUMBER, i.e. #N_A=6.022xx10^23*mol^-1#.

And so the number of formula units.........

#6.022xx10^23*mol^-1xx0.132*mol=7.97xx10^22# formula units.

How many magnesium atoms, and how many chlorine atoms?