What is the empirical formula for the compound that has 46 grams of sodium, 64 grams of sulfur, and 48 grams of oxygen?

1 Answer
Aug 6, 2016

"Na"_2"S"_2"O"_3Na2S2O3

Explanation:

Your tool of choice here will be the Periodic Table of Elements.

Grab one and look for the molar mass of sodium, "Na"Na, sulfur, "S"S, and oxygen, "O"O. Notice that you have

M_("M Na") ~~ "23 g mol"^(-1)MM Na23 g mol1

M_("M S") ~~ "32 g mol"^(-1)MM S32 g mol1

M_("M O") ~~ "16 g mol"^(-1)MM O16 g mol1

This tells you that the sample given to you contains

46 color(red)(cancel(color(black)("g"))) * "1 mole Na"/(23color(red)(cancel(color(black)("g")))) = "2 moles Na"

64 color(red)(cancel(color(black)("g"))) * "1 mole S"/(32color(red)(cancel(color(black)("g")))) = "2 moles S"

48 color(red)(cancel(color(black)("g"))) * "1 mole O"/(16color(red)(cancel(color(black)("g")))) = "3 moles O"

Now, in order to write the empirical formula of the compound, you must find the smallest whole number ratio that exists between its constituent elements.

Since the 2:2:3 ratio is already in its smallest whole number form, you can say that the empirical formula of the compound is

color(green)(|bar(ul(color(white)(a/a)color(black)("Na"_2"S"_2"O"_3)color(white)(a/a)|)))