Can anyone help my daughter with her homework. She needs to know how to calculate a balanced equation in science and cant remember how to do this. we have looked in science text book but cant follow it. Does anyone know a simple way of doing this. She needs to know how to convert this: CaCl2 + 6H2O + Na2CO3 = CaCO3 or calcium chloride crystals + distilled water + Sodium Carbonate = Calcium carbonate. She needs someone to explain in simple terms what to do please. Graham

You need the same number of elements on each side of the equation.

You have 1 Ca, 2 Cl, 12H, 9O, 2Na and a C.

you need to multiply it all to round it up to whole amounts of each.

CaCl2 + 6H2O + Na2CO3 = CaCO3

The is one Ca on each side, so thats ok to start with. However, the chlorine is missing, so the equation is wrong to start with. Judging by the sodium carbonate, im guessing there is NaCl, or salt, missing.

So, i'll add that in:

CaCl2 + 6H2O + Na2CO3 = CaCO3 + NaCl


Now then. Ca adds up, but one Cl and one Na is missing. Double the salt to even it up:

CaCl2 + 6H2O + Na2CO3 = CaCO3 + 2NaCl


I cant actually see what the H2O is doing, as it doesnt seem involved at all, however, its there at the beginning so it needs to be there at the end:

CaCl2 + 6H2O + Na2CO3 = CaCO3 + 2NaCl + 6H2O


Now, this is a start but i suspect still wrong, as the water part doesnt work out. But, its still a start!

Try this site, hopefully helps
http://richardbowles.tripod.com/chemistry/balance.htm

The equation you gave doesn't work as their isn't any hydrogen on the right hand side. So first thing to do is get that sorted.

As joel says it makes NaCl, I think the water is coming from the fact they are aqueous solutions, but as it just appears on both sides you can forget about it as it doesn't participate in the reaction. Or you could think of it cancelling out, so to speak.

Another site is
http://misterguch.brinkster.net/eqnbalance.html
a bit American but might be easier to understand.

p.s. My wife is a Chemistry teacher so I'm being fed bits of information here

[Edited on 12/1/07 by iank]

[Edited on 12/1/07 by iank]

This equation is to do with precipitation and ending up with a solid form of calcium carbonate. Does this make any difference to anything? Graham

I'd have to guess at CaCl2 + 6 H2O + Na2CO3 = CaCO3 + 2NaCl + 6H2O. As said the water is merely to make it aqueous, as it wouldn't really work dry. The calcium carbonate is dissolved in the water, but comes out in caves etc as stalagtites. Presumably something to do with acid(ic) rain?

Crystals can store water, but the equation still needs it there to make sense.

This is possibly one of those annoying situations where we know more between us than the poor teacher, who doesnt understand the equation anyway! lol

[Edited on 12/1/07 by JoelP]

I think you would end up with the calcium carbonate precipitated in a solution of sodium chloride.The Sodium chloride is soluble and the calcium carbonate is less soluble so precipitates out of the solution.
Paul.

One point, how old is your daughter? As this determines how much detail you want/need.

Won't they combine to make salt and bicarbonate of soda?