Lattice arrangements and Calculations 1920

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1. Which of the following unit cells is an example of a face-centered unit cell? *

All of them

B and C

2. Given the unit cell of NaCl, how is it that there is 4 chloride ions? *

There are 6 halves of ions (6 x .5) and 4 quarters (4 x .25)

There are 12 on the edge (12 x .25) and 1 in the body position

There are 6 halves on each side ( 6 x 1/2) and 8 eighths in the corners (8 x 1/8).

There are 4 halves of ions (4 x .5) in the face and 12 halves (12 x .5)

None of the above choices are correct

3. In calculating the mass of of the unit cell using the chloride ions, why do we divide by Avogodro's number? *

So that we know the mass of a mole of cubic cells.

So that we know the mass per 1 chloride ions.

Because a mole of ions fits in the cubic cell

Because we need a mole of cubic cells to study since they are so small.

4. In the absence of X-ray crystallography, explain how the length of the cubic cell is determined? *

The radius of 2 Cl ions plus the radius of 2 Na ions

The is 1 diameter of a Na ion and 2 radii of the Cl ion on the edge.

There is 2 radii of Na ions and 1 diameter of the Cl ion.

There is a total of 4 Cl atoms and 4 Na ions in the cubic cell.

None of the above choices are correct.

5. Which of the following is a correct diagram of the face centered unit cell of copper? *

6. Answer the problem below: *

PLease round to 3 sig figs and write in scientific notation like this: 6.02x1023. No UNITS!

7. The edge length (lattice constant) of Aluminum is 405 pm. A picometer is 1 x 10-12 m or you can think of a picometer is 1 / 1,000,000,000,000 of a meter (1 trillionth of a meter). Please convert 405 pm to centimeters (cm). Remember that you are going from a small unit (pm) to a larger unit (cm). *

PLease round to 3 sig figs and write in scientific notation like this: 6.02x1023. No UNITS!

8. Calculate the volume of the unit cell of Aluminum (in cm3 or centimeters cubed) *

PLease round to 3 sig figs and write in scientific notation like this: 6.02x1023. No UNITS!

9. Given that Al has a face- centered cubic structure, calculate the mass (g or grams) of a single unit cell of Aluminum. *

NO UNITS IN ANSWER!

PLease round to 3 sig figs and write in scientific notation like this: 6.02x1023. No UNITS!

10: Calculate the density of an Al cubic cell (in g/cm3 or grams per centimeters cubed) *

PLease round to 3 sig figs. No UNITS!

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