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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: kinzdaniels on November 20, 2018, 02:54:04 PM

Title: Stoichiometry lab help
Post by: kinzdaniels on November 20, 2018, 02:54:04 PM

I am absolutely terrible at stoichiometry and I’m unable to figure out this lab I have for chemistry. The chemical equation they gave is:

Na2CO3(aq) + CaCl2*2H2O = CaCO3(s) + 2NaCl(aq) + 2H2O(aq)

It then asks me to:
calculate how many moles of CaCl2•2H2O are present in 1.50 g of CaCl2•2H2O

then calculate how many moles of pure CaCl2 are present in the 1.50 g of CaCl2•2H2O.

I think I got the first part which I think is .0102 mol, but I’m not sure about the second part of the question.

But then it asks:
From the previous step determine how many moles of Na2CO3 are necessary to reach stoichiometric quantities.

 From that calculation, determine how many grams of Na2CO3 are necessary to reach stoichiometric quantities.

This just completely lost me and I have no idea what to do. Could someone please try and help me, I’d like to try and understand this if I could.

Title: Re: Stoichiometry lab help
Post by: Borek on November 20, 2018, 03:16:38 PM

Quote from: kinzdaniels on November 20, 2018, 02:54:04 PM

then calculate how many moles of pure CaCl2 are present in the 1.50 g of CaCl2•2H2O.

Is it a different number?

How many moles of Ca in one mole of CaCl₂? (exactly the same principle)

Quote

I think I got the first part which I think is .0102 mol

Looks OK.

Quote

From the previous step determine how many moles of Na2CO3 are necessary to reach stoichiometric quantities.

How many moles of Na₂CO₃ react with one mole of CaCl₂?