How do you determine the formula weight of "Na"_2"CO"_3"Na2CO3 and "Ca"_3("PO"_4)_2"Ca3(PO4)2?

1 Answer
Meave60
Jun 30, 2017

See the explanation.

Explanation:

To determine the formula weight of a substance, multiply each element's subscript by its atomic weight on the periodic table, then add the result. Reminder: no subscript is understood to be 11.

Formula weight of "Na"_2"CO"_3":Na2CO3:

(2xx22.990 "u Na")+(1xx12.011 "u C")+(3xx15.999 "u O")="105.998 u Na"_2"CO"_3",(2×22.990u Na)+(1×12.011u C)+(3×15.999u O)=105.998 u Na2CO3,

where "u"u is the symbol for unified mass unit.

Formula weight of "Ca"_3"(PO"_4)"_2:Ca3(PO4)2:

(3xx40.078 "u Ca")+(2xx30.974 "u P")+(8xx15.999 "u O")="310.174 u Ca"_3"(PO"_4)"_2(3×40.078u Ca)+(2×30.974u P)+(8×15.999u O)=310.174 u Ca3(PO4)2

If you need molar masses, replace "u"u with grams/mole, or g/mol.

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