Impossible chem question, help? involves percentage by mass?

Question

Ok I have no idea how to approach this:

If 10.0g of washing soda crystals, of formula Na2CO3.10H20, are heated to remove all the water, what would the mass loss be?

I thought of maybe working out percentage by mass of H20, but how would you do that and if you did, what what you do then to get the answer??

Please, can you answer with explanations and details if you can.

Thanks a lot.

Answer 1

So if you have 10g of Na2CO3.10(H2O) you can work out how many moles of the stuff you have.

moles = mass / molar mass

molar mass is 23 + 12 + 3.(16) + 10.(16) + 20 = 263 g/mol

moles = 10 / 263 = 0.038 moles of the stuff

you heat it and dry it and whatever to remove the 10(H2O)

Now you can find the mass you removed

mass = moles x molar mass
= 0.038 x molar mass of 10(H2O)

= 6.8g! WOW - that's a lot of water in them thar crystals

If you want, you can express this as a percentage... 68% of the mass of your Sodium Carbonate crystal is water!

Answer 2

not impossible... find moles of original compound....find its molecular weight... that many gram of compound gives out 18*10 gram of water...so that much is loss. Rest is sodium carbonate
You can loss in absolute or ratio.
Do not ask all lines duly solved.. you will get better idea when you go thru all steps yourself.

Answer 3

depends on how long washed, temperature of water, altitude.