Using the average atomic masses given inside the front cover of this book, calculate the number of atoms present in each of the
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<span>The velocity of a wave is calculated by v = λf. From this equation we can take the frequency f = v / λ and substitute in the energy equation to find a new equation for the calculation of the energy from the wavelength:
E = hc / λ</span>
To calculate the photon energy, in eV (Electrovolt), when we have the value of the wavelength λ (necessarily given in Å - angstrom), we use an alternative equation given by:
Data: 670.8 Å
Solving:
To calculate the photon energy, in eV (Electrovolt), when we have the value of the wavelength λ (necessarily given in Å - angstrom), we use an alternative equation given by:
Data: 670.8 Å
Solving:
<u>Answer:</u> The percentage yield of aspirin is 38.02 %.
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
.....(1)
- <u>For salicylic acid:</u>
Given mass of salicylic acid = 10.09 g
Molar mass of salicylic acid = 138.12 g/mol
Putting values in equation 1, we get:
The chemical equation for the formation of aspirin follows:
As, acetic anhydride is present in excess. So, it is considered as an excess reagent.
Thus, salicylic acid is a limiting reagent because it limits the formation of products.
By Stoichiometry of the reaction:
1 mole of salicylic acid produces 1 mole of aspirin.
So, 0.0730 moles of salicylic acid will produce = of aspirin
Now, calculating the mass of aspirin from equation 1, we get:
Molar mass of aspirin = 180.16 g/mol
Moles of aspirin = 0.073 moles
Putting values in equation 1, we get:
To calculate the percentage yield of aspirin, we use the equation:
Experimental yield of aspirin = 5.0 g
Theoretical yield of aspirin = 13.15 g
Putting values in above equation, we get:
Hence, the percent yield of aspirin is 38.01 %.