Saturday, April 24, 2010

Converting moles into grams?

1. 1 mole of HCl is equal to __________g(grams) of HCl


2. 1 mole of CaCl2 is equal to __________ g of CaCl2


3. 2 moles of (NH4)2SO4 (ammonium sulfate) is equal to _________g of ammonium sulfate














i dont understand how to do these at all anyhelp will be appreciated

Converting moles into grams?
A mole can be expressed as gram/mole equal to the Molecular weight of the compound: -





1)...HCl = 1 + 35.5 = 36.5g/mol. (1xH + 1xCl)


2)...CaCl2 = 40 + 71 = 111g/mol. (2xCa + 2xCl)


3)...(NH4)2SO4 = 28 + 8 + 32 + 64 = 132 x 2 moles


....... = 264g/mol. ........2 x (2xN + 8xH + 1xS + 4xO).
Reply:Multiply the number of moles by the Mr (= sum of Ar values).


I'll do the first one:





1 x (1 + 35.5) = 36.5g HCl
Reply:Err. Just find the molecular weight of the Substance.





In HCl, its 1 + 35.5 = 36





So gram molar mass of HCl is 36.5,





ie 1 mole of HCl = 36.5 grams,





Similarly for CaCl2 and ammonium sulphate. I don't remember the molecular weight of Ca. Was it 40 or 41?








The basic thing is, that you find the molecular weight and write a " gram " next to the number you get. That is the gram molecular weight of the compound, and that is the mass of 1 mole of that substance.





If you have 2 moles, multiply the gram molecular weight by 2, and so on. So gram molar weight of a substance is the weight of 6.023 * 10^23 ions / atoms/ molecules of that substance, and is the same as moleculer weight, only usually, when you say molecular weight, its in amu. and GMW is in grams.
Reply:couple of resources for you ...
Reply:1) 36.5g





2) 111g





3) 132 x 2 = 264g
Reply:2) 1 mole CaCl2





Ca = 40.078 g/mole Cl 35.5 g/mole





Ca + 2 Cl = 40.078 +2(35.5) = 111.078 g/mole





so you'd need 111.078 g





3) 2 moles (NH4)2SO4





N=14.0067 H=1.0079 S= 32.066 = 15.9994





NH4 = 14.0067+4(1.0079)= 18.038 g/mole


SO4 = 32.066 + 4(15.9994)= 96.0636 g/mole





(NH4)2SO4 = 2(18.038)+96.0636 = 132.1396 g/mole





2 mole would be 264.2792 g

daphne

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