Chemical Forums
Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: diamorph on November 09, 2008, 09:34:42 PM
-
a) Prepare 500mL stock solution that has a concentration of 400ppm NO3- form KNO3. How many g of KNO3 dose you need to weigh out.
b) Make a 100ppm NO3- working stock solution, form the stock solution, and name it A. How are you planning to make the A and how much are you going to make (how much are you going to use later).
c) Make a dilution series from A, make 250mL of each of the dilutions a-e
How many mL of A is needed for each dilution?
Dilution a b c d e f
ppm NO3- 0 2.0 4.0 8.0 12 16
mL A
i can probably, maybe work out the rest as long as i figure out a)...
-
ppm = mass substance * 106
mass solvent
So, you tell me how much you need.
-
sorry, got a little distracted, that wasn't what i meant to post, it's this one:
The content of Manganese in a steel sample should be determined by spectroscopy. Mn is oxidized to permangante.
1. A stock solution (stock I) that should be 1000mg Mn per Liter is prepared. How much KMnO4 do you have to weight out for 500ml of stock I solution?
2. By dilution a stock II solution containing 100mg Mn/L is prepared. How much of stock I do you have to pipette in order to make 250ml of stock II solution?
3. The calibration curve has to be from 0 to 20 mg Mn/L. How many ml of stock II do you need for 100ml of the following standard solutions?
Std. No. 1 2 3 4
Mg/L 2,00 5,00 10,0 20,0
i dont get the first part.
its a simple calculation, i know, i just dont understand the steel, Mn to MnO oxidation, etc thing.
-
its a simple calculation, i know, i just dont understand the steel, Mn to MnO oxidation, etc thing.
So start assuming there is not first statement, imagine question starts with
1. A stock solution (stock I) that should be 1000mg Mn per Liter is prepared. How much KMnO4 do you have to weight out for 500ml of stock I solution?