E 29 part c

[venning-1J]

Im having trouble figuring out part c.

E.29 A chemist measured out 8.61 g of copper(II) chloride tetrahydrate, CuCl2 4H2O.
(a) How many moles of CuCl2 4H2O were measured out? 0.0417 mol
(b) How many moles of Cl ions are present in the sample? .0834 mol
[i](c) How many H2O molecules are present in the sample? [/i]
(d) What fraction of the total mass of the sample was due to oxygen? 0.31

I attempted to multiply 0.0417 x 4 x 6.0022x10^23 but I am not getting the answer, which the book states is 1.00 x 10^23.

[RahilVaknalliDis3A]

You are on the right track. I believe there is a simple calculation error since you are multiplying the number of moles of water molecules with the wrong number. Avogradro's constant is 6.022 x 10²³ and not 6.0022 x 10²³

[Christy Zhao 1H]

I'm confused with part d. How would I go about to find what fraction of the total mass of the sample was due to oxygen?

[jorineraymundo2h]

It's easier to answer the question if you think of the problem's pathway.

Mass (CuCl2 4H2O) -> Moles (CuCl2 4H20) -> Moles (4H20) -> Molecules

(8.16g/206.53gmol^(-1)) x 4molesH20 x (6.0221x10^(23)) = 1.00 x 10^(23)

I hope this helps!

[Aman Sankineni 2L]

For part d, you must figure out the mass of oxygen as part of the formula. Since there is 4 oxygen atoms, the mass of oxygen is 16x4=64. By dividing that by the total mass of the formula, 206.446, you can figure out what fraction of the total mass was due to oxygen. 64/206.446=.310008 or 31%.

[Amy Kumar 1I]

For part d, you must figure out the mass of oxygen as part of the formula. Since there is 4 oxygen atoms, the mass of oxygen is 16x4=64. By dividing that by the total mass of the formula, 206.446, you can figure out what fraction of the total mass was due to oxygen. 64/206.446=.310008 or 31%.

Do you not have to take into account that there were 8.61 g of copper(II) chloride tetrahydrate initially?

[Kassidy Ford 1I]

Because it is just the percentage of mass of oxygen, then the original mass of 8.61g copper(II) chloride tetrahydrate doesn't matter. No matter how many grams of the sample you have the percentage mass of oxygen should always be the same because of the molar ratios. Correct me if I'm wrong!

[Kassidy Ford 1I]

Because it is just the percentage of mass of oxygen, then the original mass of 8.61g copper(II) chloride tetrahydrate doesn't matter. No matter how many grams of the sample you have the percentage mass of oxygen should always be the same because of the molar ratios. Correct me if I'm wrong!

[Aman Sankineni 2L]

Because it is just the percentage of mass of oxygen, then the original mass of 8.61g copper(II) chloride tetrahydrate doesn't matter. No matter how many grams of the sample you have the percentage mass of oxygen should always be the same because of the molar ratios. Correct me if I'm wrong!

Yup, this is right. Molar ratios always remain the same. No matter the mass of the copper(II) chloride tetrahydrate, the percent composition of oxygen remains the same.

[Cooper_Geralds_3B]

Hi, we did this problem in discussion today but I missed the answers. For part a) I ended up getting 0.0423 moles and I was wondering why I got a different answer than posted above? I multiplied 8.61 g * (1 mol/ 202.484 g/mol). I got 202.484 g/mol by adding up the molar mass.

[Adalia 3E]

Hi, we did this problem in discussion today but I missed the answers. For part a) I ended up getting 0.0423 moles and I was wondering why I got a different answer than posted above? I multiplied 8.61 g * (1 mol/ 202.484 g/mol). I got 202.484 g/mol by adding up the molar mass.

I got 206.45g/mol when adding up the molar mass, maybe it has to do with that?

[Cooper_Geralds_3B]

Hi, we did this problem in discussion today but I missed the answers. For part a) I ended up getting 0.0423 moles and I was wondering why I got a different answer than posted above? I multiplied 8.61 g * (1 mol/ 202.484 g/mol). I got 202.484 g/mol by adding up the molar mass.

[isha dis3d]

Hi, we did this problem in discussion today but I missed the answers. For part a) I ended up getting 0.0423 moles and I was wondering why I got a different answer than posted above? I multiplied 8.61 g * (1 mol/ 202.484 g/mol). I got 202.484 g/mol by adding up the molar mass.

I think it has to do with the molar mass. Specifically it would be:
Cu: 63.55
Cl: 35.45 x 2 = 70.9
H 2 0: 18.02 x 4= 72.08

Adding all these is 206.5 g/mol. 8.61 g divided by this gives us 0.0417 mol Cucl2 4H20.

[205484435]

Hi, I was having trouble on part b of this problem, of someone can walk me through it I would really appreciate it.

[azurexrose]

We know the chemist measured out 8.61 g of CuCl2 4H2O, which has a molar mass of 206.51 g/mol. This means there are 0.0417 moles of CuCl2 4H2O. Since each molecule of CuCl2 4H2O contains 2 Cl ions, when this dissolves in water, the chlorine ions separate, so there are a total of 0.0834 moles of Cl.

[amreen_sandhu1k]

Hi I am having trouble with part d of this problem I would really appreciate if someone could walk me how they solved that.