Question

What is the molar mass of `"sodium carbon decahydrate"`, `Na_2CO_3*10H_2O`?

Answer 1

Got a Periodic Table?

Explanation:

Of course you have. Look up the elemental masses and add them together, i.e. for `Na_2CO_3*10H_2O`. Failing that just google the molecules, and their molecular masses will be quoted somewhere.

Answer 2

The formula mass of sodium carbonate decahydrate, `"Na"_2"CO"_3*"10H"_2"O"`, is `"286 u"`.

Explanation:

Calculate formula mass of `"Na"_2"CO"_3*10"H"_2"O"`.

Multiply the subscript of each element by its relative atomic mass, `"A"_r"`, on the periodic table. No subscript is understood to be `1`. In the case of `"10H"_2"O"`, you will need to also multiply by the coefficient `10`. I'm going to round the `"A"_r"` for each element to a whole number. Your instructor may want you to use more digits.

`(2xx"23 u Na")+(1xx"12 u C")+(3xx"16 u O")+(10xx2xx"1 u H")+(10xx1xx"16 u O")="286 u Na"_2"CO"_3*10"H"_2"O"`

If the molar mass is required, it is numerically equal to the formula mass in g/mole.