AS Chem Moles Question

Anyone help please?

"Sodium carbonate is manufactured in a two-stage process as shown by the equations below.

NaCl + NH3 + CO2 + H20 ----> NaHCO3 + NH4Cl

2NaHCO3 ----> Na2C03 + H20 + CO2

Calculate the maximum mass of sodium carbonate which could be obtained from 800g of sodium chloride."

Couldn't you do a direct calculation based on "One mole of NaCl makes one mole Na2CO3" or would you have to do something different because it's a two-stage process?

Reply 1

idiopathic

Overall equation would be..
2NaCl + 2NH3 + 2CO2 + 2H20 ----> 2NaHCO3 + 2NH4Cl

2NaHCO3 ----> Na2C03 + H20 + CO2

=> 2NaCl + 2NH3 + 2CO2 + 2H20 -> 2NH4Cl + Na2C03 + H20 + CO2

=> 2NaCl + 2NH3 + CO2 + H2O -> 2NH4Cl + Na2CO3

I think this equation should work?

Reply 2

fairieboi

sadly it doesn't work like that ;p the NaHCO3 made in the first reaction needs to be doubled up for the second reaction so you need to do it seperately

stages for working it out would have to be:
a) work out how many moles of NaCl that is, which = the moles of NaHCO3 produced in the first stage
b) divide that number of moles by 2 to find out how many moles of Na2CO3 are produced in the second stage (which is a 2 -> 1 reaction)
c) work out how much that is in mass

unless i've gone wrong somewhere that's the quickest way to do it

Reply 3

fairieboi

hah, i really need to learn to type faster - i always get beaten to it ;p

Reply 4

aiman

Moles of NaCl = 800/58.5 = 13.68 moles
Moles of NaCl = Moles of NaHCO3 = 13.68 moles
Mole ratio of NaHCO3 : Na2CO3 = 2:1
Therefore moles of Na2CO3 = 13.68/2 = 6.84 moles
Molar mass of Na2CO3 = (23*2)+(12)+(3*16) = 106 gm
Mass of Na2CO3 produced = 106*6.84 = 725 gm

I hope this helps.