[hslove142331]

Silver forms face-centered cubic crystals. The atomic radius of a silver atom is 144 pm. Consider the face of a unit cell with the nuclei of the silver atoms at the lattice points. The atoms are in contact along the diagonal. Calculate the length of an edge of this unit cell.

I don't understand.. even, I don't know the equation for this problem.
This question seems like geometry science.
I am really not good at geometry.
please help me
Please explain to me that how can I solve this problem.
Thank you

[Unknown008]

Hmm, I think that the question is more about math...

Ok, considering that the atoms touch at diagonals, that means that they form a triangle.



It's simple pythagoras.

Can you find the length of the last side of this triangle now?

[hslove142331]

I found answer
Thank you :)
But, here more queation.. Its more harder than before question

1.The unit cell edge of a substance (1 monatomic cation:1 monatomic anion) having a crystal lattice identical to that of sodium chloride has a length of 586.2 pm. The cation of the substance has a radius of 89 pm. What is the diameter of the anion?

2.Calculate the interplanar spacing (in picometers) that corresponds to defracted beams of X rays at θ = 33.4o, if the X rays have a wavelength of 136. Pm. Assume n = 1.

Please help like previous question.
Thanks..
These questions are hard to understand.Thanks
Please Please help

[hslove142331]

I did second problem, and my answer was correct ;)

But, I am still confusing on first question

Please help

[Unknown008]

I'm not too sure about it...

The total (addition of 2 diameters) give 586.2 pm.
The radius of cation is 89. So, its diameter is (89*2) = 178 pm
The diameter of anion is (586.2-178) = 408.2 pm

For the second one, I never saw such a question in chemistry, but it sounds like a physics question I did. Do you use the formula : ?

[hslove142331]

I did it, Thanks

[Unknown008]

Hey, I would like to learn too, and confirm if what I did was right! Could you tell how you did them?

[hslove142331]

The unit cell edge of a substance (1 monatomic cation:1 monatomic anion) having a crystal lattice identical to that of sodium chloride has a length of 586.2 pm. The cation of the substance has a radius of 89 pm. What is the diameter of the anion?

One cell edge equals 2 cation radii plus 2 anion radii.
586.2-(89*2)=408.2pm
They asking that diameter

So, answer is 408.2pm
It was really easy question, when I got understand problem.
You and my ways were totally correct way to solve that problem.

Thanks :)

[hslove142331]

At a molecular level, explain why in osmosis there is a net migration of solvent from the side of the membrane less concentrated in solute to the side more concentrated in solute by selecting all that apply.

1.The side of the membrane that is less concentrates in solute is more concentrated in solvent.

2.The side of the membrane that is less concentrates in solute is less concentrated in solvent.

3.The escaping tendency of the solvent increases with its concentration.

4.The difference in escaping tendency results in a net migration of solvent from the side less concentrated in solute to the side more concentrated in solute.

5.The difference in escaping tendency results in a net migration of solvent to the side less concentrated in solute from the side more concentrated in solute.


I think number 5 & 1 is correct
What do you think about this problem?
Thanks

[Unknown008]

I agree for 1 and 5 all right.

[hslove142331]

How about number 3?

[Unknown008]

While it's partly true, it also depends on the concentration of the solute at the other side of the membrane. No matter how concentrated it is,if the other one is as concentrated, the net migration of the solvent molecules will be zero.

That depends now, if the person who made that question was looking at 3 like this, or not. I hesitated with it myself, but I finally decided not to put 3, because I consider it only partly true.

[hslove142331]

Oh.. okay I tried 1&5 and it says its not correct.
So, I was so confusing that I think that 1&5 is correct... I don't know why
They saying that incorrect..
Thanks

[Unknown008]

Sure? 1 and 5 do make sense, in opposition to the others...

1. If the solute is in small concentration, it means you have few particles in much solvent, and hence, solvent is more concentrated.

2. See no.1, it can't be. If you reduce the number of particles of solute, and the number of solvent by the same amount (according to the solute:solvent ratio), the concentration will be the same

3. I already explained my thoughts

4. I think I misread the sentence earlier. The solvent will move from less concentrated solution to more concentrated, so as to make both equally concentrated. (less concentrated having less solvent will become more concentrated and it is the same the other way round)

5. As opposed to 4.

Okay, so I go for 1 and 4. Sorry for the mistake earlier. :o