2.76 #g# of #K_2CO_3# was treated by a series of reagents so as to convert all of its carbon to #K_2Zn_3[Fe(CN)_6]_2#. Calculate the weight of the product?

1 Answer
Jul 18, 2015


The mass of the product is 1.16 g.


All you really have to do to solve this problem is figure out how much carbon you had in the 2.76-g sample of potassium carbonate.

Once you do that, you use the fact that all of the carbon present in the potassium carbonate sample is now a part of the final product.

So, use carbon and potassium carbonate's molar masses to determine the percent composition of carbon in the compound

#(12.011cancel("g/mol"))/(138.206cancel("g/mol")) * 100 = "8.69% C"#

Potassium carbonate contains 8.69 g of carbon for every 100 g of compound. This means that your sample contained

#2.76cancel("g"K_2CO_3) * "8.69 g C"/(100cancel("g"K_2CO_3)) = "0.2398 g C"#

All this carbon is now found in the final product. Once again, use molar masses to determine the carbon percent composition of #K_2Zn_3[Fe(CN)_6]_2#.

Keep in mind, however, that you have a total of 12 carbon atoms in the final product!

#(12 * 12.011cancel("g/mol"))/(698.235cancel("g/mol")) * 100 = "20.64% C"#

Once again, this tells you that you have 20.64 g of carbon for every 100 g of product.


#0.2398cancel("g C") * "100 g product"/(20.64cancel("g C")) = color(green)("1.16 g product")#