totally confused?

Question

ok so i have the formula for a reaction of sodium carbonate and calcium chloride dihydrate to produce a precipitate of calcium carbonate.

Na2CO3(aq) + CaCl2. 2H2O(aq) -> CaCO3(s) + 2NaCl (aq) + 2H2O

So i have 1.0g of CaCl2. 2H2O. I put it in a beaker. How many grams of Na2CO3 for a full reaction to produce a precipitate of calcium carbonate?

Would it be 1.0g as well?

oh i discovered something about mole ratio but i don't really know..

btw im trying to figure out a stoichiometry question.

Answer 1

Stoichiometry requires 3 steps:
(1) convert grams of given substance, CaCl2.2H2O in this case, to mole of given substance
(2) mole ratio, given substance vs. desired substance
mole ratio is simply the coefficient ratio (the number in front of the formula)
e.g. Na2CO3 vs NaCl = 1 mol Na2CO3 / 2 mol NaCl
CaCl2.2H2O vs CaCO3 = 1 mol CaCl2.2H2O / 1 mol CaCO3
(3) convert mole of desired substance to grams of desired substance

So, first you need to convert 1.0 g of CaCl2.2H2O to mole before using the ratio.
You need something called Molar Mass. CaCl2.2H2O has the molar mass of (40.08 + 2*35.45 + 4*1.01 + 2*16.00 = 147.02 g/mol), those numbers are from the Periodic Table.)
Mole of CaCl2.2H2O = 1.0 g * 1 mol/147.02g = 0.0068 mol

Since CaCl2.2H2O and CaCO3 is 1 to 1 ratio
That means you need 0.0068 mol of CaCO3
Molar Mass of Na2CO3 is (40.08 + 12.01 + 3*16.00 = 100.09 g/mol)

0.0068 mol * 100.09 g/mol = 0.68 g CaCO3 is produced

Answer 2

Moles are important in chemistry. Some people have some difficulty with the concept. A mole is just a really large number of atoms or molecules (6.02 x 10^23 to be exact).

Think of a more familiar number. A dozen. Molarity and the ratio required and the corresponding weights are similar. Say you have 24000 pounds of cars and you need windshield wipers for them. How many pounds of windshield wipers do you need? Each car weighs 2000 pounds and you can figure out that you have 12 cars. If each car needs 2 windshield wipers, then you need 24 wipers. If each wiper weighs a half a pound then you need 12 pounds of wipers.

Molarity and moles are the same way. You can't tell how much of one component you need until you divide out the molecular weight of the compound and figure out how many you have. Then you need to figure out how many of x go with how many of y. (in your problem statement it is a 1:1 ratio). Then you need to know how much each y weighs to get back to mass.

By the way. Asking how many grams of one compound you need to react with another compound is like asking how many pounds of wipers you need to go with how many pounds of cars... seems a little crazy :-)

Answer 3

Calcium Carbonate Dihydrate

Answer 4

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