How do calculate the the following problems?

Note:
"v" signifies an upside down caret ^
v2 signifies the subscript of 2
v6 signifies the subscript of 6

Calculate each of the following:
A. number of Li atoms in 4.5 mol of Li
B. number of CO v2 molecules in 0.0180 mol of CO v2
C. Moles of Cu in 7.8 * 10^21 atoms of Cu
D. Moles of C v2 H v6 in 3.75 * 10^23 molecules of C v2 H v6

1 Answer
Raknos
Oct 26, 2017

All of these can be solved by using unitary method.

A. #1# mol of Li #= 6.022 * 10^23# atoms.
hence, #5.4# mol Li #=5.4 * 6.022 * 10^23# atoms
# = 3.252 * 10^24# atoms.

B. #1# mol of #CO_2# #= 6.022 * 10^23# molecules.
Hence, #0.0180# mol of #CO_2# #= 0.0180 * 6.022 * 10^23# molecules.

C. #6.022 * 10^23# atoms Cu = #1# mol Cu.
#1# atom Cu = #1/(6.022*10^23)# mol Cu.
hence, #7.8 * 10^21# atoms of Cu = #7.8 * 10^21 * 1/(6.022*10^23)# mol Cu.

D. #6.022 * 10^23# molecules of #C_2H_6# = #1# mol #C_2H_6#.
#1# molecule of #C_2H_6# = #1/(6.022 * 10^23)# mol #C_2H_6#.
Hence, #3.75 * 10^23# molecules of #C_2H_6# = #3.75 * 10^23 * 1/(6.022 * 10^23)# mol #C_2H_6#.

I haven't bothered to do the complete calculations, you can do them yourself.

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