Question #e5db6

1 Answer
Stefan V.
May 2, 2015

Assuming you're referring to grams of each element, you'd need 106 g of sodium and 69.0 g of chlorine.

You need to determine the percent composition of sodium chloride, that way you'll know how many grams of sodium and how many grams of chlorine would that much sodium chloride contain.

To do that, use the molar masses of sodium, chlorine, and sodium chlorine

#(23.00cancel("g/mol"))/(58.44cancel("g/mol")) * 100 = "39.4% Na"#

#(35.45cancel("g/mol"))/(58.44cancel("g/mol")) * 100 = "60.6% Cl"#

This tells you that, for every 100 g of sodium chloride, you get 39.4 g of sodium and 60.6 g of chlorine.

As a result, 175 g of sodium chloride would contain (rounded to three sig figs):

#175cancel("g NaCl") * "39.4 g Na"/(100cancel("g NaCl")) = color(green)("69.0 g Na")#

#175cancel("g NaCl") * "60.6 g Cl"/(100cancel("g NaCl")) = color(green)("106 g Cl")#

SIDE NOTE If you're looking for moles, not grams, use the molar masses of the two elements to go from grams to moles.

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