Homework: E1, 6th Ed.

[michellebui_3L]

The questions asks to find the length of the fiber when we are given a radius of 144 pm and 1.00 mol of Ag. How would we solve this problem to find the length of the fiber?

[Albert_Luu3K]

Dear Michelle Bui,

I also had trouble with this question because my answer was always far off from the actual answer. Soon I came to realize my mistake. You start off by multiplying Avogadro's number to the amount of moles of Ag to the get the number of atoms you have in the fiber. Once you have that number, multiple it by 288pm because 144pm is the radius and you want the diameter since diameter is the length that goes from one end to another. Once you have that length, you need to convert the units from pm to km. Hope that helps!

Your son,
Albert Luu

[Catly Do 2E]

It gives you the radius, but you need the diameter to get the length of the chain. So 2 x 144 pm = 288 pm. 1 mol of Ag means there are 6.022 x 10^23 atoms of Ag. Then you multiply (6.022 x 10^23 atoms of Ag)(288 pm)= 1.73 x 10^26 pm. Then, you convert to km, which is 1.73 x 10^11 km.

[Dong Hyun Lee 4E]

Adding onto the question above. I understand how the answer would come out but using the SI measurements, would it be incorrect to leave the answer in meters and not kilometers. And if it would be incorrect could someone explain to me why that would be the case?

[danicatran4]

Adding onto the question above. I understand how the answer would come out but using the SI measurements, would it be incorrect to leave the answer in meters and not kilometers. And if it would be incorrect could someone explain to me why that would be the case?

I have the same question. Wouldn't you leave the answer in meters since that's the fundemental SI unit?

[MaryBanh_2K]

Hi Michelle,
This is how I approached this problem:

1. Find unknown and known.
Known: 1 mol of Ag and Avogadro's number of atoms (6.022x10^23 atoms)
Unknown: length of fiber

2. Calculate the number of atoms in 1 mol Ag by using Avogadro's number.
1 mol Ag * (6.022*10^23 atoms Ag/1 mol Ag)= 6.022*10^23 Ag atoms

3. You are given the radius but we need to find the diameter of each atom. Therefore, since the radius is 144pm, the diameter is two times that
144pm*2= 288pm

4. Finally, multiply the two values you got from steps 2 and 3 to get the total length and then convert to meters.
( 6.022*10^23 Ag atoms* 288pm) 1.73*10^26pm
1.73*10^26pm*(1m/10^12pm)= 1.73x 10^14m

The final answer is 1.73x 10^14m.

Hope this helps!