ap chem unit 3 pt 2 test

calculate the mass percent of Co in the 0.630 g sample of the ore.

(6.50x10^-4)x58.93/1.00= 0.0383 0.0383/0.630 x100= 6.08%

what is the [Co2+] in the solution if the absorbance of a sample of the solution is 0.74?

0.0130 (0.0125 to 0.0135)

calculate the number of moles of Co2+ in the 50.0 mL solution.

0.05000x0.0130/1.00= 6.50x10^-4

A wavelength of 510 nm corresponds to an approximate frequency of 6 x 10^14 s^-1. What is the approximate energy of one photon of this light?

4 x 10^-19 J

If the absorbable of the mixture is 0.20 at 453 nm, how many moles of Fe2+ were present in the 100. mL sample?

4x10^-6 mol

which of the following is closest to the frequency of the light with the photon energy of 3.3x10^-19?

5.0x10^14

which statement correctly compares what occurs when molecules absorb photons in the microwave region with what occurs when molecules absorb photons in the infrared region?

Microwave photons cause the molecules to increase their rotational energy states, whereas infrared photons cause the molecules to increase their vibrational energy states.

infrared spectroscopy is a useful tool for scientists who want to investigate the structure of the certain molecules. which of the following best explains what can occur as a result of a molecule absorbing a photon of infrared radiation?

The energies of infrared photons are in the same range as the energies associated with different vibrational states of chemical bonds. Molecules can absorb infrared photons of characteristic wavelengths, thus revealing the types and strengths of different bonds in the molecules.

Beta-carotene is an organic compound with an orange color. The diagram above shows the ultraviolet spectrum of beta-carotene. which of the following statements is true about the absorption bands in the spectrum?

The two main absorption bands are associated with transitions in electronic energy levels. The band in the region corresponding to shorter wavelengths shows a lower absorbance than the band in the region corresponding to longer wavelengths.

N2 molecules absorb ultraviolet light but not visible light. I2 molecules absorb both visible and ultraviolet light. Which of the following statements explains the observations?

Visible light does not produce transitions between electronic energy levels in the N2 molecule but does produce transitions in the I2 molecule.

Based on the calibration curve shown below, what is the concentration of the solution in micro moles per liter?

between 5.2 and 5.6

if the student measured the absorbance of the solution at a wavelength of 650 nm, would the absorbance be greater than, less, than, or equal to the absorbance of the solution at 559 nm?

less than, because 599 nm is the maximum wavelength and anything that is higher than that number would automatically make the absorbance lower.

if the student mixed 10 mL of distilled water with 10 mL of the sample, would this distilled solution have an absorbance grater than, less than, or equal to the absorbance of the original solution?

less than, because it has a lower concentration, therefore, the solution would have a lower absorbance than the original because of Beer's law.

Using the wavelength information provided above, what is the color of the light?

orange

which of the following is the most likely explanation for the discrepant data in trial 4?

the concentration of the solution was actually lower than 0.150 M.

The student made the standard curve above. Which of the following most likely caused the error in the point the student plotted at 0.050MCo2+(aq) ?

there was distilled water in the cuvette when the student put the standard solution in it.