A solution prepared by dissolving 25.8 mg of benzene (78.11 g/mol) in hexane (86.16 g/mol) and diluting to 250 mL had an absorption peak at 256 nm and an absorbance of 0.266 in a 1.000-cm cell.
Question: What is the concentration of benzene solution?
Question: What is the percent transmittance?
Question: What is the molar absorptivity coefficient of benzene?
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1. (benzene) = mols/L = (0.0258/78.11)/0.250 = ?
2. log A = log 1/T or 100/%T
3. A = abc
0.266 = a*1*c from 1 above. Substitute and solve for a
I get the 1 and 3, but in number 2. what is T = Po/P before passing and after passing, so what is the T? is it the 256nm and 0.266?
Nvm i already got it, 0.266=-logT derive, 10 raise to -0.266 thanks.
To answer these questions, we need to understand the concepts of concentration, absorbance, transmittance, and molar absorptivity.
1. Concentration of benzene solution:
The concentration of a solution is usually expressed in terms of molarity (moles of solute per liter of solution). In this case, we have the mass of benzene (25.8 mg) and its molar mass (78.11 g/mol). We can use this information to calculate the moles of benzene in the solution and then convert it to molarity.
First, let's calculate the moles of benzene:
moles = mass / molar mass = 25.8 mg / 78.11 g/mol = 0.3303 mmol
Next, let's convert mmol to moles:
moles = 0.3303 mmol / 1000 = 0.0003303 mol
Finally, let's calculate the concentration in molarity (M):
Molarity (M) = moles / volume (in liters)
Given that the volume is 250 mL (or 0.250 L):
M = 0.0003303 mol / 0.250 L ≈ 0.00132 M
Therefore, the concentration of the benzene solution is approximately 0.00132 M.
2. Percent transmittance:
Transmittance is a measure of the amount of light that is transmitted through a sample. It can be calculated from the absorbance using the formula:
Transmittance = 10^(-absorbance)
In this case, the absorbance is given as 0.266. Plugging the value into the formula:
Transmittance = 10^(-0.266) ≈ 0.610
To calculate the percent transmittance, we multiply the transmittance by 100:
Percent transmittance = 0.610 * 100 ≈ 61.0%
Therefore, the percent transmittance of the solution is approximately 61.0%.
3. Molar absorptivity coefficient of benzene:
The molar absorptivity coefficient (ε) is a constant that reflects the substance's ability to absorb light at a specific wavelength. It is usually given with units of L/mol·cm. We can calculate it using the equation:
Absorbance = ε * concentration * path length
In this case, the absorbance is 0.266, the concentration of benzene is 0.00132 M, and the path length is given as 1.000 cm. Plugging in these values:
0.266 = ε * 0.00132 M * 1.000 cm
To isolate ε, we can rearrange the equation:
ε = absorbance / (concentration * path length)
ε = 0.266 / (0.00132 M * 1.000 cm) ≈ 201.5 L/mol·cm
Therefore, the molar absorptivity coefficient of benzene is approximately 201.5 L/mol·cm.