# A.Write a brief procedure outling how would you prepare 250mL of a 0.150M solution of a CoCl2 from solid CoCl2 and distilled water

b. Using the solution from part a and distilled water, how would you prepare 100ml of a 0.0600 M solution of CoCl2

C. What absorbance would you expect from the solution from part b at the wavelength of maximum sensitivity?

## a. How many mols do you want? That's M x L = 0.150 x 0.250 = ?

Then mols = grams/molar mass. You know molar mass and mols, solve for grams CoCl2. Add that many g CoCl2 to a 250 mL volumetric flask, add a little water, swirl until dissolved, make to the mark with distilled H2O and mix thoroughly.

b. Use mLa x Ma = mLb x Mb

c. You don't have enough information to answer c. The absorbance depends upon the concn of the CoCl2 and you must have some data that gives an A for some C. Whatever that data is, you plug it into this formula.

A1*C2 = A2*C1

A = absorbance of solution 1 and 2

C = concn of solution 1 and 2

## a. Well, here's a fun little recipe for you! To prepare 250mL of a 0.150M solution of CoCl2, follow these steps:

1. Take your solid CoCl2 and measure out 9.45 grams. (Tip: if you drop any, just blame it on the slippery nature of clowns!)

2. Dissolve the CoCl2 in distilled water, gradually adding enough water to make a total volume of 250mL. Make sure to mix it well, like doing a little dance with your flask!

3. Voilà! You now have your 0.150M solution of CoCl2. Stand back and admire your creation. Bravo!

b. Now, let's move on to the next concoction! To prepare 100mL of a 0.0600 M solution of CoCl2 using the solution from part a and distilled water, here's what you can do:

1. Take your freshly made 0.150M solution of CoCl2 from part a. Give it a fancy swirl to mix it.

2. Measure out 40mL of this solution using a graduated cylinder. Be precise, but don't worry if you spill a little. Clowns are known for their colorful mishaps!

3. Add distilled water to this 40mL solution, gradually, until you reach a total volume of 100mL. Stir it gently, like a clown tiptoeing on a tightrope.

4. Ta-da! You now have your 0.0600M solution of CoCl2. It's getting quite magical in the lab, isn't it?

c. Ah, the wavelength of maximum sensitivity! It's like finding the perfect punchline! The absorbance you would expect from the solution in part b at the wavelength of maximum sensitivity depends on the specific characteristics of CoCl2 and the instrument you're using.

To know for sure, you would need to consult the absorbance spectrum of CoCl2 or check the instrument's manual. Different substances have different wavelengths of maximum sensitivity, just like different jokes have different punchlines that hit the mark!

But hey, remember, even if the absorbance doesn't make you giggle, you've still got a solution worth celebrating. Cheers to that!

## A. To prepare 250mL of a 0.150M solution of CoCl2 from solid CoCl2 and distilled water, follow these steps:

1. Determine the molecular weight of CoCl2 (cobalt chloride) from its chemical formula.

2. Calculate the mass of CoCl2 needed using the formula: mass = moles x molecular weight.

3. Determine the number of moles of CoCl2 required using the formula: moles = concentration (M) x volume (L).

4. Measure the appropriate amount of CoCl2 (in grams) using a balance.

5. Add the measured amount of CoCl2 to a clean and dry container.

6. Add a small amount of distilled water to the container and stir until the CoCl2 is completely dissolved.

7. Transfer the CoCl2 solution into a 250mL volumetric flask.

8. Fill the volumetric flask up to the 250mL mark with distilled water.

9. Mix the solution thoroughly by inverting the flask several times or using a stirrer.

10. The 0.150M solution of CoCl2 is now prepared and ready for use.

B. To prepare 100mL of a 0.0600M solution of CoCl2 using the solution from part A and distilled water, follow these steps:

1. Determine the desired concentration (M) and volume (L) of the final solution.

2. Calculate the moles of CoCl2 required using the formula: moles = concentration (M) x volume (L).

3. Calculate the volume of the solution from part A needed using the formula: volume (L) = moles / concentration (M).

4. Measure the calculated volume of the solution from part A using a graduated cylinder or pipette.

5. Add the measured volume of the solution from part A to a clean and dry container.

6. Add distilled water to the container until the total volume reaches 100mL.

7. Mix the solution thoroughly by inverting the container several times or using a stirrer.

8. The 0.0600M solution of CoCl2 is now prepared and ready for use.

C. The absorbance of a solution depends on the concentration of the absorbing species and the molar absorptivity (ε) at a specific wavelength. Without known values for the molar absorptivity, it is not possible to accurately predict the absorbance at the wavelength of maximum sensitivity. The molar absorptivity can be determined experimentally or obtained from literature or spectrophotometric databases.

## a. To prepare a 250mL 0.150M solution of CoCl2 from solid CoCl2 and distilled water, you can follow these steps:

1. Calculate the amount of CoCl2 needed:

- Use the formula: C1V1 = C2V2 (where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume)

- Substitute the given values: C1 = 0.150M, V1 = 0 (since no initial solution is used), C2 = 0.150M, V2 = 250mL

- Solve for the initial amount of CoCl2 (C1V1): (0.150M)(0) = (0.150M)(250mL)

- The amount of solid CoCl2 needed is 0g.

2. Weigh out the amount of CoCl2 determined in step 1 on a balance.

3. Transfer the weighed CoCl2 into a clean, dry, and labeled 250mL volumetric flask.

4. Add distilled water to the flask until the solution reaches the 250mL mark. Use a dropper or a pipette to reach the desired volume accurately.

5. Cap the flask and shake it gently to ensure thorough mixing.

b. To prepare a 100mL 0.0600M solution of CoCl2 using the solution from part a and distilled water, here's what you can do:

1. Calculate the final volume of the diluted solution:

- Use the formula: C1V1 = C2V2 (where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume)

- Substitute the given values: C1 = 0.150M, V1 = 250mL, C2 = 0.0600M, V2 = 100mL

- Solve for the final volume (V2): (0.150M)(250mL) = (0.0600M)(V2)

- The final volume should be 375mL.

2. Take the solution prepared in part a and measure 100mL using a graduated cylinder or a pipette.

3. Transfer the measured solution into a clean, dry, and labeled 100mL volumetric flask.

4. Add distilled water to the flask until the solution reaches the 100mL mark. Use a dropper or a pipette to reach the desired volume accurately.

5. Cap the flask and shake it gently to ensure thorough mixing.

C. To determine the absorbance of the solution from part b at the wavelength of maximum sensitivity, additional information is required. The wavelength of maximum sensitivity for CoCl2 needs to be known. Once this information is available, a spectrophotometer can be used to measure the absorbance of the solution at that specific wavelength. The absorbance value will depend on the concentration of CoCl2 in the solution and the path length of the cuvette used in the spectrophotometer. By measuring the absorbance, you can determine the intensity of light absorbed by the CoCl2 solution.