To determine the rate of reaction for the decomposition of aspirin a student wei
ID: 528178 • Letter: T
Question
To determine the rate of reaction for the decomposition of aspirin a student weighted out 0.0650 g of aspirin (MW=180.57g/mol) and transferred it to a test tube. In the test tube he added 1.00 ml of n-propanol and 10.00ml water. The test tube with the mixture was first heated in a water bath of 92 degree C for 6 mins, then removed from the bath water to cool down. To determine the amount of salicylic acid obtained in the aspirin degradation, first, 5.00 ml of 0.025 M Fe(NO3)3 was added to obtain the violet complex of iron-salicylate and the second the absorbance of the violet solution was measure at 525 nm with a S-20 spectrometer and found to be 0.304.
what is the molarity of the aspirin solution prepared, before being heated to 92 degree C?
Standard stock solution of salicylic acid is prepared by dissolving 0.0799 g of salicylic acid (MW=138.12 g/mol) in water and diluted to 50.00 ml
-what is the concentration of salicylic acid in the stock solution expressed in mol/L?
The following standard salicylic acid solution ( 2.31 x 10^-4, 4.63 X 10^-4, 6.94 x 10^-4, 9.26 X 10^-4, and 11.6 x 10^-4 mol/L) were prepared from the stock solution ( each solution was prepared in an amount of 10.0 mL). The absorbance of the stand solutions is obtain from the S-20 spectrometer at the wavelength if 525 nm as shown in the data table below:
Standard Volume of Stock Concentration of salicylic acid Absorbance
Solutions solution used (ml) mol/L
1 2.31 x 10^-4 0.070
2 4.63 X 10^-4 0.150
3 6.94 x 10^-4 0.200
4 9.26 X 10^-4 0.250
5 11.6 x 10^-4 0.360
Explanation / Answer
1) aspirin M.W. = 180.57
to prepare solution, 0.650 gms of aspirin is dissolved in 10 ml of water and 1 ml of n-propanol
the concentration of aspirin is
1000 * 0.650 / (10+1) * 180.57 = 0.36 mol.
= 3.6 * 10-1
2) similarly salicylic acid M.W. is 138.12
0.0799 gms of salicylic acid is dissolved in 50 ml of water.
The concentration os salicylic acid stock solution is
1000 * 0.0799 / 50 * 138.12 = 0.011 mol
= 1.1 * 10-2
the absorbance of the stock solution is 0. 304.
3) standard salicylic acid solutions, 5 nos. are prepared in the following way :
1st solution concentration is .2.32 * 10-4 mol / L and its absorbance is 0.070
2ndt solution concentration is .4.63 * 10-4 mol / L and its absorbance is 0.150
3rd solution concentration is .6.94 * 10-4 mol / L and its absorbance is 0.200
4th solution concentration is .9.26 * 10-4 mol / L and its absorbance is 0.250
5th solution concentration is .11.6 * 10-4 mol / L and its absorbance is 0.360
the final question is not clear.
but, still it can be seen that the question can be that
' how many ml of stock solution is taken to make up the standard solutions'-
it can be seen that
0.64 uL of stock solution is used to prepare standard solution 1.
.1.28 uL of stock solution is used to prepare standard solution 2.
1.92 uL of stock solution is used to prepare standard solution 3.
2.56 uL of stock solution is used to prepare standard solution 4.
3.2 uL of stock solution is used to prepare standard solution 5.
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