How many grams of H20 will be needed to produce .45 mole of Ca(OH)2?

Question

You dont have to give me the answer, but please tell me how to approach the problem, or how to solve it.

Answer 1

well you need to set up a factor label equasion

Here is the equation for the reaction:

CaCO3+H2O---------->Ca(OH)2+CO2

You will notice that the ratio of H2O to Ca(OH)2 is one, since both of the compounds do not have a number in fron of them it is understood to be one

1:1

Okay, now we're setting up the factor label oroblem. You will notice that the top and bottom labels will cancel each other out.

1. You want to know grams of H20. so that is how you start off your probelm

grams H2O=

2. You put in the value given in the problem next, for the first part to be equal to.

grams H2O=.45mole Ca(OH)2

3. Ok, you will notice that right now you are in moles of Ca(OH)2, but really you want to somehow get to moles of H20. You can do this by comparing the ratio of H2O to Ca(OH)2 (You got it from the equasion remember?) 1:1 This is how you show that

grams H2O=.45 mole Ca(OH)2 x 1mole H20
1 mole Ca(OH)2


4. Remember I said the top and bottom labels will cancel each other out, so you want to cancel the "moles" label out, by putting moles on the bottom of the next equasion. I'll show you

grams H2O=.45 moles Ca(OH)2 x 1mole H2O x
1 mole Ca(OH)2 1mole H2O

5. You see how the moles of H2O would cancel out the moles of H20, don't worry about the numbers just the labels. Well, you may wonder what should go on top of the 1 mole of H20. Well a mole of any compound is equal to its gram formula mass (THe mass of every atom added up in the compound)

There are 2 atoms of hydrogen in H2O with a mass of 1 gram each, so the mass for all accounted Hydrogen atoms is 2 grams

There is one atom of Oxygen in H2O with a mass of 16 grams, so the mass for all accounted for Oxygen atoms is 16 grams

The gram formula massis then 18, since hydrogen are two grams and the oxygen is one. Now put this answer into your equasion.

grams H2O=.45 moles Ca(OH)2 x 1mole H2O x 18 grams H20
1 mole Ca(OH)2 1mole H2O

6. You know your factor label equasion is done because you ended with what you started with. You wanted grams of H20 and you ended with grams of H20. Ig you zigzag from side to side you will notice tha labels will cancel out, not the numbers, the labels.

Now, all you have to do is solve your eqaution, hte numbers on the bottom represent division.


So you do

.45 X 1 divided by 1 x 18 divided by 1

Your answer is 8.1 grams of H20!!!!

i;M SORRY, FOR SOME REASON YAHOO ANSWERs will not line up the equasions like they are supposed to be.....
iF YOU ARE STILL THOROUGHLY CONFUSED WITH THIS CONCEPT, JUST IM ME. i'M DEFINATELY WILLING TO HELP YOU TO THE BEST OF MY ABILITIES.

Answer 2

CaCO3+H2O=Ca(OH)2+CO2atomic wt of Ca=40,O=8,H=1
0.45 mol of Ca(OH)2=0.45*(40+16+2)=26.1 g
58 gms of Ca(OH)2 will need 18 gms of water
so 26.1 gms will need (26.1/58)*18=8.1 gms