Question

How many molecules of H2O are there in 1.0 g of H2O?

Answer 1

in 1.0 grams of H2O. okay so..

You are given grams (mass). To go from mass to molecules, you have to convert:

Mass -> Moles -> Molecules.

To go from mass to moles, Divide by the molecular weight.
To go from moles to molecules, multiply by 6.02 x 10^23.

Answer 2

convert to moles. then use avogradro's number \(6.022 \times 10^{23}\frac{ atoms }{ mol }\)

Answer 3

I do not know how to do this ..

Answer 4

Sure you do ;) Let's take it step by step.

You are given 1 gram of H2O, and need to divide this by the molecular weight.
The molecular weight can be found by adding up all the individual masses of the atoms.

How many atoms of Hydrogen are in H2O?
How many atoms of Oxygen are in H2O?

Multiply the number of atoms of Hydrogen by the atomic mass of hydrogen.
Multiply the number of atoms of Oxygen by the atomic mass of oxygen.
Add these two values together, what do you get?

Answer 5

2 atoms in Hydrogen and 1 atom of Oxygen.
atomic mass of hydrogen is 1
2*1=1
atomic mass of oxygen is 15.9994
15.994*1=15.9994
Added together is 16.9994

Answer 6

Do you have it now? Or do you still need help?

Answer 7

I don't know if 16.9994 is the answer?

Answer 8

Hang on. I'll figure it out

Answer 9

Okay thank you

Answer 10

No. Obviously no. It's way too small.

Answer 11

I have no clue what I am doing

Answer 12

Do you know what a mole is?

Answer 13

Not really

Answer 14

That might be your trouble. A mole of any compound or element is the molecular weight in grams. So if you had a scale and wanted to weigh out a mole of water, you would weigh out 18 g because 2H=2, O = 16 and the molecular weight is 18

Answer 15

Do you understand that?

Answer 16

No, I am so sorry

Answer 17

Do you know how to find molecular weight?

Answer 18

I looked it up online

Answer 19

So I take that to be a yes?

Answer 20

Do you have a periodic table?

Answer 21

I looked up the weight online. and I do, yes

Answer 22

Find the molecular weight of HCl

Answer 23

36.46094

Answer 24

So a mole of HCl is 36.46094 grams.

Answer 25

Now here is the next important point: a mole of "stuff" has 6.023 x 10^23 molecules in it.

Answer 26

That's Avagadro's number. That is something you cannot reason out you have to learn it.

Answer 27

So lets say I have some carbon. A mole of carbon is 12 grams. I have 24 grams. How many moles is that?

Answer 28

12

Answer 29

2

Answer 30

Yes. Good. Now remember each mole is 6.023 x 10^23 molecules so how many molecules of carbon do I have?

Answer 31

I suppose I do not understand how 6.023 X 10^23 works because if there are 2 moles how exactly do I work that in?

Answer 32

If you have 1 mole of "stuff", you have exactly 6.023 x 10^23 molecules.

If you have 2 moles of stuff, you would multiply Avogadro's number by 2.

Answer 33

Would you agree that 2 moles is twice as much as 1 mole and so I should multiply by 2?

Answer 34

^

Answer 35

And
\[2(6.023 \times 10^{23)}=12.046 \times 10^{23}\]

Answer 36

So that is the number of molecules in 2 moles of carbon.

Answer 37

Ok. dimensionx will help you now. Too many cooks.

Answer 38

so we aren't really solving the entire equation because when I did that I had a ginormous number

Answer 39

@Mertsj sorry didn't mean to tread on you xD

blahhhh,
We are taking it step-by-step ;)

Answer 40

So we know that we have 2 Hydrogens and 1 Oxygen.

2 x Hydrogen
1 x Oxygen

2 x (1) = 2
1 x (16) = 16
Total Molecular Weight = 18

Answer 41

Do you understand how I got this value?

Answer 42

yes.

Answer 43

So why isn't this problem done yet?

Answer 44

because I do know how to apply this... I am thinking at 18 is the answer. I am sorry It is just not clicking.

Answer 45

18 grams is 1 mole of water. How many moles is 9 grams of water?

Answer 46

.5

Answer 47

That would be 9/18 right?

Answer 48

yes

Answer 49

How many moles is 3 grams of water?

Answer 50

Just tell me the fraction.

Answer 51

50 g

Answer 52

3/18

Answer 53

I think I see a pattern here: I will draw it because I want you to see it too.

Answer 54

okay!