[VAM]

Hello everyone, here is the problem i have:

The element nickel crystallizes in a face-centered cubic crystal, with a0 = 3.5238 pm.  The atomic weight is 58.69 g/mol.  Avogadro’s number is 6.02214×10^23mol-1. What is the calculated density of Ni, in g/cm3?

The Answer given is: 8.909g/cm^3

Here is my work:

1. Convert a0 from picometers to centimeters

3.5238 pm x 1cm/10^10pm = 3.5238 x 10^-10 cm

2. Cube a0 to get volume in cm^3

(3.5238 x 10^-10 cm)^3 = 4.375 x 10 ^ -29 cm^3

3. Calculate mass of the sample

Because its a face centered cube:

4(58.69 g/mol)
_____________            =            3.89 x 10^-22 g
6.02214×1023mol-1


4. Since D = m/v

D = (3.89 x 10^-22 g)/(4.375 x 10 ^ -29 cm^3) = 8909423.353 g/ cm^3


Im getting the right values but the decimal point seems to be shifted a bit too far....

Can anyone take a look at what i did wrong?

Thanks.

[cth]

The unit for your value of a₀ is wrong. It should not be picometers, but it is angstroms: 3.5238 A.
If you want it in picometers: 352.38 pm.

[VAM]

The unit for your value of a₀ is wrong. It should not be picometers, but it is angstroms: 3.5238 A.
If you want it in picometers: 352.38 pm.

hmm...after recalculating the problem at the value you gave me, 352.38 pm, i have gotten the correct answer. My prof must have given us the wrong value. Thank you very much! Ive been staring at this problem trying to find errors in my math for 1 hour....