I am a little bit confused on what I am supposed to do. The instructions say to prepare 250 mL of this solution by measuring out in grams the amount of PFT using a 250 mL volumetric flask. Then it says I have to add dI water until te meniscus hits the full mark on the flask, then it says to calculate the actual molarity of the solution. Am I supposed to multiply the molarity by the liters given to me to find the grams of PFT I am supposed to use? How would you go about this?
1 Answer
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It is quite trivial. Just calculate how many moles of potassium ferrocyanide trihydrate you need to measure out (n = C x V), then multiply with molar mass to see how many grams you need to measure out. After measuring the sample on analytical balance, quantitavely transfer it to the volumetric flask. Add some water and dissolve the sample. After homogenizing the solution, add water carefully to the full mark. You can't actually calculate the exact molarity of the prepared solution: you need to determine it experimentally, by performing a standardization with silver-nitrate standard using chromate salt as an indicator.
