How many grams of K2Cr2O7 to dissolve it in 1 liter Distilled water to obtain 50 ppm of Chromium? to become aqueous solution, Is there a specific equation to apply? Thanks
Unless I'm missing something, for 50 mg/L you simply dissolve 50 mg of potassium dichromate in 1 liter of water. The partial volume of the potassium dichromate is too small to make any perceptible difference in such a large volume of water.
Adam B Shapiro Thanks to you Doctor, but yes there is a little equation suggested by researchers in the lab for preparation, according to your Great Experience, can we use it or not? After applying the answer is 0.28 grams or as you said simply dissolve 50 mg (0.05 grams)
Ali Safaa I think that depends on what purpose you need that solution for. For example, if you needed to make a solution with a concentration of just the chromium(IV) ion in an analytical study, you would need half of that mass you calculated above because for every mole of potassium dichromate, there are two moles of chromium(IV). Here I post the stoichiometric relationship that I made to calculate that concentration and I hope it makes sense.
Errami Ahmed answer is correct. 52 is the atomic weight of Cr and 294.18 is the molecular weigh of potassium dichromate. 2 is the stechiometric conversion factor.
To prepare a 50 ppm (mg/L) solution of Chromium from K2Cr2O7, you can follow the steps below:
Calculate the molar mass of K2Cr2O7: K2Cr2O7 = 2(K) + 1(Cr) + 7(O) = 294.18 g/mol
Calculate the mass of K2Cr2O7 required to make a 50 ppm solution: 50 ppm = 50 mg/L To prepare 1 L of a 50 ppm solution, you would need: 50 mg/L x 1 L = 50 mg
Convert the mass of K2Cr2O7 required to moles: 50 mg / 294.18 g/mol = 0.170 moles
Dissolve the calculated amount of K2Cr2O7 in 1 L of distilled water to obtain a 50 ppm (mg/L) solution of Chromium.
The equation to calculate the required mass of solute to prepare a given concentration in a given volume of solvent is:
mass (in grams) of solute = concentration (in mg/L) x volume (in L) / 1000
So, in this case, we can use the above equation as follows:
mass of K2Cr2O7 = 50 mg/L x 1 L / 1000 = 0.05 g
Therefore, you would need to dissolve 0.05 g of K2Cr2O7 in 1 L of distilled water to obtain a 50 ppm (mg/L) solution of Chromium.