A question in my review book is as follows:
2,92 grams of Cr2O3 is extracted from a 12,78 gram sample of Silver Chromate Ag2CrO4. What is the atomic weight of the Chromium?
The answer in the back of the book uses the periodic table molar mass values for oxygen and silver. But it seems to me that the question could produce various answers depending on which isotope of silver is found in the sample. In my mind it is impossible to determine the actual atomic weight of the chromium in question without first knowing the atomic weights of the other elements as well (oxygen is fairly straight forward since it is virtually always 16).
The atomic mass of silver provided is the average of several different isotopes. So if the isotope in question is, say, 109Ag then the mass percentage of chromium in the sample would be slightly less than if the silver were, say, Ag-107. This would slightly affect the calculated value of chromium's atomic mass. It seems odd that the question is asking for a specific value for atomic weight but assumes average molar mass values. Wouldn't the resulting value be based on the average molar mass for silver?
ChemBuddy | 
Chem Reddit | 
Topic: Is this a fair atomic mass question? (Read 2521 times)