G. C. 1-1 Identification of Metals 7 G. C. I-I: GROUP DISCUSSION QUESTIONS

1. Which way turned out to be the most accurate to determine the density of the metal, calculation from a single data point, slope of the manually drawn or the computer-created graph? What do you think, why?

2. A sample of an unknown alloy has a density of 10.582 g/cm³. If its components come from the five met als from today's lab, can you estimate what the predominant metal is? If so, which is it?

3. Describe how you would modify the experiment if you had a metal that floated on the water. How would you change the experiment to obtain the volume of the metal?

4. Since the metal sample is a cylinder is there another way you could determine the volume of the cylin der other than via displacement of water? If so, describe how you would go about doing so and include any relevant equations. Hint: Think back to geometry.

5. Do you think determining the density using this method would be more accurate than those performed by today's experiment? Hint: Consider different errors in determining volume via water displacement versus the method described in Question 4 above.

1. Which way turned out to be the most accurate to determine the density of the metal, calculation from a single data point, slope of the manually drawn or the computer-created graph? What do you think, why?

2. A sample of an unknown alloy has a density of 10.582 g/cm³. If its components come from the five met als from today's lab, can you estimate what the predominant metal is? If so, which is it?

3. Describe how you would modify the experiment if you had a metal that floated on the water. How would you change the experiment to obtain the volume of the metal?

4. Since the metal sample is a cylinder is there another way you could determine the volume of the cylin der other than via displacement of water? If so, describe how you would go about doing so and include any relevant equations. Hint: Think back to geometry.

5. Do you think determining the density using this method would be more accurate than those performed by today's experiment? Hint: Consider different errors in determining volume via water displacement versus the method described in Question 4 above.

first, consult an activity series chart to determine if al is more reactive than fe. it is, so it will replace the fe. now, one can continue with the problem.

next, make sure you have a correctly balanced equation.

3feo + 2al ==> 3fe + al2o3

now, determine which reactant (feo or al) is in limiting supply.

moles feo present = 125 g x 1 mole/71.8 g = 1.74 moles

moles al present = 25.0 g x 1 mole/26.98 g = 0.927 moles

since from the balanced equation, it take 3 mol feo for every 2 mol al, al will be limiting.

you can determine this simply by dividing moles of each by their coefficient in the balanced equation. for example: 1.74/3 = 0.58 and 0.927/2 = 0.464. al is less, so it is limiting.

finally, using the stoichiometry in the balanced eq. determine mass of fe that can be produced from 0.927 moles of al.

0.927 moles al x 3 moles fe/2 moles al x 55.8 g/mole = 77.6 g

i believe the answer is three water molecules