In Section 6.2d, we saw that the pK, of an acid is equal to the pH of the solution at which half the acid has dissociated into its conjugate base. UV-vis spectroscopy can be used to measure the relative concentrations involved if the acid or conjugate base absorbs UV-vis light. With this in mind, suppose that a particular acid has a Amax of 312 nm. The figure here shows the absorbance at that wavelength as a function of pH. What is the pk, of the acid? 3 4 6 7 8 10 11 12 pH Absorbance at 312 nm

In Section 6.2d, we saw that the pK, of an acid is equal to the pH of the solution at which half the acid has dissociated into its conjugate base. UV-vis spectroscopy can be used to measure the relative concentrations involved if the acid or conjugate base absorbs UV-vis light. With this in mind, suppose that a particular acid has a Amax of 312 nm. The figure here shows the absorbance at that wavelength as a function of pH. What is the pk, of the acid? 3 4 6 7 8 10 11 12 pH Absorbance at 312 nm

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...

See similar textbooks

Similar questions

SOLVE STEP BY STEP IN DIGITAL FORMAT Explain the underlined paragraph, make it extensive and unambiguous, support its foundations in biochemistry and quantum mechanics. The sample substance used is 1,1-diphenyl-2-picryl-hydrazyl (DPPH). This organic compound is a relatively stable free radical which has an unpaired valence electron at one atom of the nitrogen bridge. The orbital motion of the electron is almost cancelled by the molecular structure. Therefore the g-factor of the electron is almost equal to that of a free electron. In its polycrystalline form the substance is very well suited for demonstrating electron spin resonance because it has an intense ESR line, which, due to exchange narrowing, has a small width.
The absorbance of an ionic aqueous solution is 0.387. What is the ratio of intensities of the passed light over the incident light for that solution? I/IO =
10. The Raman spectroscopy instrument records data and then plots signal intensity vs. raman shift. What are the actual wavelengths that are (1) emitted by the laser within the instrument that is directed at the sample and (2) that are sent back to the instrument due to a Raman interaction with your sample of dry ice that has a Raman active IR band at 1300 cm³¹.
To determine the amount of iron thiocyanate in a polluted water sample. Weprepared a series of standard solutions for calibration graph. For 1 ppm standard solution, absorbance reading recorded 0.155. Calculate the amount of light transmitted (in percent) for 2 ppm standard solution.
A student creates a sports drink by dissolving 5.0 g of powder in 250 mL of water. The green colour of the drink is due to the presence Green Dye X, which has a lambdamax of 630 nm. A calibration curve (absorbance versus concentration) at lambdamax is created for varying concentrations (mM) of Green Dye X which has the equation y = 26.8x. If 1.0 mL of the sports drink is diluted to 10. mL with water, then the absorbance is measured to be 0.340, what is the mass percent of Green Dye X in the drink powder if the molecular weight is 418.4 g mol-1?
A calibration curve is made for the absorbance as a function of concentration of blue dye (in mg/L). The slope of the curve is 0.131; the y-intercept is -0.01869; the correlation is 0.993. If a consumer sample has an absorbance of 0.120 on the same instrument, what is its concentration of blue dye, in mg/L? a. 0.034 b. 0.935 c. 0.993 d. 1.06
A student calibrated the mini-spectrophotometer with a blank solution, and then went to check their solution. They got a fingerprint on the cuvette while filling it. Because of this, the expected reading for the absorbance would be too high which would cause the calculated value of K, to be too high
Which of the following statements concerning spectroscopy is correct? A) Concentration of a solution is directly proportional to the % of photons transmitted. B) Salt plates are often used in IR spectroscopic measurements because they are transparent in that region. C) Molar absorptivity is a constant for given species, regardless of concentration or wavelength. D) Fluorescence excitation is usually red-shifted from emission wavelength. E) 2 or more statements are correct. The absorbed energy to enable vibrational level transition falls within which wavelength range A) radio wave B) microwave C) IR D) X-ray E) UV and visible
Answer all of the following about colours and UV-Visible Spectra. a) The very idealized UV-Visible Spectrum of a violet solution of [Sc(H2O)6]** is shown: 3. wavelength A chemist carries out the following reaction: [Sc(H2O)s]* + Z yellow solution [ScZe]* (n depends on Z) Is Za solution of NH3 or a solution of NaBr? Justify your answer. Predict the shift (if any) in the UV-Visible Spectrum for [ScZ6]". Justify your answer. b) The following hydroxide species are all known: Mn(OH)42 Co(OH)4 Zn(OH). • Assign a colour to each species. Possible choices: blue, red, colourless Note: some choices may be used more than once, some not at all. Justify your answer for any one of the species.
As the pH changes, how will the absorbance change at the wavelength of the isosbestic point?
Describe how a deuterium lamp can be used to provide background correction for an atomic absorption spectrum.
If a solution has an absorbance value of 0.325 at a wavelength of 450 nm, what is the percent transmittance of this solution at this wavelength?