How do you calculate the molar mass of each of the following compounds?

#Cu(OH)2#
#MgO#
#Mg(NO_3)_2#
#NaCl#
#(NH_4)_2SO_4#
#H_2SO_4#
#Ca_3(PO_4)_2#
#NH_4NO_3#

2 Answers
Sep 12, 2016

Answer:

I will answer one, and from the answer you can use the same method tom work out the rest: #Ca_3(PO_4)_2# = 310.177 g/mol

Explanation:

You need to look up the atomic weight of each element (these can be found by asking google for the atomic weights):

#Ca_3# means there are three Ca; #PO_4# means there is one P and 4 oxygen, the #()_2# means there two #PO_4#. So, substituting in the values:

#Ca_3(PO_4)_2#
(3 x 40.078) + ((30.973762 + (4 x 15.9994)) x 2)
120.234 + ((30.973762 + 63.9976) x 2)
120.234 + (94.971362 x 2)
120.234 + 189.942724
310.177

So the answer is 310.177 g/mol

You should now be able to use the above approach to work out the answers for the other compounds.

Sep 12, 2016

Answer:

Simply add the molar masses of the individual elements.

Explanation:

For calcium phosphate, #Ca_3(PO_4)_2# we do the sum: #{3xx40.08 (Ca),+2xx31.00 (P), +8xx16.00 (O)}*g*mol^-1# #=# # 310.18*gĀ·mol^-1#.

If we had lithium phosphate, #Li_3PO_4#, what would be the formula mass? I invite you to do the rest of the salts on your list. You will need a Periodic Table to get the individual molar masses of the elements.