Hi;
I have a question here and I know what the answer is supposed to be, and I also know that I know how to do it but I can't for the life of me remember how...any help would be apprecaited. Thanks alot.
You are supplied with a soultion of mordant yellow that has a concentration of 3.3 x 10-5 M and a molecular weight of 358.3g/mol. In a 10ml volumetric flask, put 0.05g of alpha-cyclodextrin which has a molecular weight of 972.9g/mol and then fill to the mark with the mordant yellow solution. This gives a cyclodextrin/mordant yellow stock solution. What is the concentration of the cyclodextrin in the soultion, where the concentration of mordant yellow is still 3.3 x 10-5M?
Let's call alpha-cyclodextrin acdl.
mols acdl = 0.05 g/molar mass acdl.
mols acdl/0.010 L = concn in mols/L = M.
I may have missed something so check my thinking.
I was thinking the exact same thing after I posted that today... I think I was thinking it was more complicated because it had so much information, but also cause I think I read it as the total concentration, not the concentration of one. Anyways, thanks alot for your help!
To find the concentration of cyclodextrin in the solution, we can use the concept of molar concentration and the formula:
Concentration (M) = (moles of solute) / (volume of solution in liters)
First, let's find the number of moles of mordant yellow in the solution using its concentration and the volume of the solution.
Concentration of mordant yellow = 3.3 x 10^-5 M
Volume of solution = 10 ml = 10 x 10^-3 L
Moles of mordant yellow = (Concentration of mordant yellow) x (Volume of solution)
= (3.3 x 10^-5 M) x (10 x 10^-3 L)
= 3.3 x 10^-7 moles
Next, let's find the number of moles of cyclodextrin in the solution using its mass and molecular weight.
Mass of alpha-cyclodextrin = 0.05 g
Molecular weight of alpha-cyclodextrin = 972.9 g/mol
Moles of alpha-cyclodextrin = (Mass of alpha-cyclodextrin) / (Molecular weight of alpha-cyclodextrin)
= (0.05 g) / (972.9 g/mol)
= 5.14 x 10^-5 moles
Since the molar ratio between mordant yellow and alpha-cyclodextrin is 1:1 (as stated in the problem), the number of moles of cyclodextrin is also 3.3 x 10^-7 moles.
Finally, we can find the concentration of cyclodextrin using the number of moles and the volume of the solution.
Concentration of cyclodextrin = (moles of cyclodextrin) / (volume of solution)
= (3.3 x 10^-7 moles) / (10 x 10^-3 L)
= 3.3 x 10^-5 M
Therefore, the concentration of cyclodextrin in the solution is 3.3 x 10^-5 M, where the concentration of mordant yellow is still 3.3 x 10^-5 M.