# gammagirl

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1. ## IR puzzle

I was thinking "A shoulder band usually appears on the lower wavenumber side in primary and secondary liquid amines arising from the overtone of the N–H bending band: this can confuse interpretation."
2. ## IR puzzle

When obtaining an IR spectrum, a secondary amine should exhibit only one N-H stretch, however, when a student ran his sample, two N-H stretches appeared in the spectrum. What could account for this?
3. ## Which is the most correct way to determine moles?

Both are good points. Thank-you
4. ## IR spectroscopy

A secondary amine should only exhibit only one N-H stretch. However, 2 N-H stretches appeared in the spectrum. What could account for this?
5. ## Which is the most correct way to determine moles?

I used 3 mL of 95% ethanol? 3mL x 0.789/ml x mol/46.068 g = 0.0513gm OR 95gm/100ml =x/3ml, x= 2.85 gm ethanol x mol/46.068 g= 0.06187 gm

Thank-you
7. ## Henderson-Hasselbalch

The answers mentioned above are correct, but I thoroughly understand the experiment at a higher level. Therefore, the Henderson-Hasselbach case is closed.
8. ## Determine the solution to the following differential equation: dA/dt = -0.3A and A(2) = 400

I appreciate you.
9. ## Determine the solution to the following differential equation: dA/dt = -0.3A and A(2) = 400

Determine the solution to the following differential equation: dA/dt = -0.3A and A(2) = 400
10. ## gammagirl    hypervalent_iodine

Can you help with the Henderson-Hasselbalch question, please?

11. ## Henderson-Hasselbalch

Part 1: (1) Made an unbuffered stock solution of DPH-diphenhydramine (100mg/100ml) in water (2) Made ph4 buffered stock solution of DPH (3) Made ph7 buffered stock solution of DPH (4) Made a ph10 buffered stock solution of DPH Part 2: Obtain absorbance at 252 of solutions in Part 1 Part 3: Add 5ml of DPH stock solutions to 5 ml hexanes and obtain absorbances. question: even though a buffered solution at pH7 should have a 100:1 ratio of ammonium: amine, why does the absorbance of the aqueous solution after extraction have such a large difference when compared to the unextracted stock solution of DPH of ph7? question: Assuming molar absorptivity of DPH is 388L/mole cm (a) calculate the approximate conc of DPH in each stock solution, before and after extraction with hexane. (did it) (b) Why don't these values match the expected ratios based on Henderson-Hasselbach equation? (my answer: HH is valid when it contains equilibrium concentrations of an acid and conjugate base. In this lab, changing pH increases the amount of DPH moving to the organic layer from the aqueous layer, changing the expected ratios of conjugated base and acid.)
12. ## Henderson-Hasselbalch

I have another question. Even though a buffered solution at pH 7 should have a 100:1 ratio of ammonium ion: amine, why does the absorbance of the aqueous solution after extraction with hexane have such a large difference when compared to the unextracted stock solution of the amine a ph 7?
13. ## Henderson-Hasselbalch

Step 1: Creating pH 4, 7, 10 buffered stock solutions. Step 2: Obtain absorbance by spectroscopy of buffered solutions. Step 3: Obtain absorbance of stock solutions after extraction with hexanes. Step 4: calculate concentration with Beer's Law Question: Why don't these values match the expected ratios based on the Henderson-Hasselbalch equation? The difference is due to the buffer solutions are able to withstand most changes in pH and maintain a reasonably stable pH?
14. ## Henderson-Hasselbalch

When extracting diphenhydramine from hexane and calculating the concentration of diphenhydramine using the Beer-Lambert law, the ratios of NH3/NH4+ don't match the expected ratios based on the Henderson-Hasselbalch equation. Why?
15. ## Recrystallization

Only someone really smart could give an answer like that, especially since no solubility data was given in cold versus hot to hint at that issue as the main point. That explanation is the entire basis of recrystallization.