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

1 Answer
Jun 17, 2017

Answer:

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

Explanation:

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?