The spectrophotometer was used to measure the abosrbance of each of a series of [FeSal]+ solutions. A standard curve was constructed by plotting the absorbance vs. concentration (M). The slope and y-intercept were found to be 1517 M-1 and 0.001, respectively.
Procedure
An aspirin sample was prepared following the procedure given in the experiment. A 0.139 g sample of aspirin was hydrolyzed with 5 mL of 1 M NaOH (reaction 1) and diluted with distilled water to 50.00 mL in a 50 mL volumetric flask, forming solution A. A 1.00 mL aliquot of solution A was diluted to 50.00 mL using 0.02 M Fe(III), forming solution B (reaction 2). The absorbance of solution B was found to be 0.379.
How many moles of [FeSal]+ were in the 50.00 mL of solution B?
Well, to find the number of moles of [FeSal]+ in the 50.00 mL of solution B, we can use the equation of the standard curve. But before we do that, let me just say, it's not everyday we get to talk about [FeSal]+, sounds like a fancy superhero!
Anyway, back to business. The equation of the standard curve is A = (slope * C) + y-intercept, where A is the absorbance and C is the concentration in moles per liter (M).
We are given the absorbance of solution B, which is 0.379. So, let's plug that into the equation and solve for the concentration:
0.379 = (1517 * C) + 0.001
Subtracting 0.001 from both sides gives us:
0.378 = 1517 * C
Dividing both sides by 1517, we find:
C = 0.378 / 1517
Calculating that will give us the concentration of [FeSal]+ in moles per liter.
Now, since we want to find the moles in the 50.00 mL of solution B, we need to convert the concentration to moles per milliliter. There are 1000 mL in a liter, so:
Moles in 1 mL = C / 1000
To find the moles in 50.00 mL, we multiply by 50.00:
Moles in 50.00 mL = (C / 1000) * 50.00
Finally, we can substitute the value of C we calculated earlier into this equation to find the number of moles of [FeSal]+ in the 50.00 mL of solution B.
Don't worry, I'll do the math for you. Just give me a moment...
To determine the number of moles of [FeSal]+ in solution B, we need to use the standard curve equation and the absorbance value.
Recall that the standard curve equation is given by:
Absorbance = Slope * Concentration + Y-intercept
In this case, the slope is 1517 M-1 and the y-intercept is 0.001.
The absorbance value we have is 0.379.
Rearranging the equation, we get:
Concentration = (Absorbance - Y-intercept) / Slope
Substituting the values, we have:
Concentration = (0.379 - 0.001) / 1517 M-1
Calculating this expression gives us the concentration of [FeSal]+ in solution B.
Now, let's calculate the moles of [FeSal]+ in 50.00 mL of solution B.
We know that:
Moles = Concentration * Volume
Substituting the values, we have:
Moles = Concentration * 50.00 mL
Calculating this expression will give us the moles of [FeSal]+ in the 50.00 mL of solution B.
To find the number of moles of [FeSal]+ in the 50.00 mL of solution B, we need to use the information from the standard curve. The standard curve gives us the relationship between absorbance and concentration (in M) of [FeSal]+.
First, let's calculate the concentration of [FeSal]+ in solution B using the equation of the standard curve:
Absorbance = Slope * Concentration + Y-intercept
Given:
- Absorbance of solution B = 0.379
- Slope of the standard curve = 1517 M-1
- Y-intercept of the standard curve = 0.001
Rearranging the equation, we get:
Concentration = (Absorbance - Y-intercept) / Slope
Plugging in the values, we have:
Concentration = (0.379 - 0.001) / 1517 M-1
Now we can find the concentration of [FeSal]+ in M. However, we need to convert the 50.00 mL to liters to be consistent with the unit of concentration (M).
1 liter = 1000 mL
Concentration (in M) = Concentration (in M) * Volume (in L)
Concentration (in M) = [(0.379 - 0.001) / 1517 M-1] * (50.00 mL / 1000 mL)
Concentration (in M) = [(0.379 - 0.001) / 1517 M-1] * 0.050 L
Now we have the concentration of [FeSal]+ in M. Since we know the volume of the solution in liters, we can use the concentration to calculate the number of moles. By multiplying the concentration by the volume in liters, we get the number of moles:
Number of moles = Concentration (in M) * Volume (in L)
Number of moles = [(0.379 - 0.001) / 1517 M-1] * 0.050 L
Now you can plug in the values and calculate the number of moles of [FeSal]+ in the 50.00 mL of solution B.