Exercise: MOLES

1) How many moles ⁴⁰K are contained in 10 mg K-feldspar with a K2O-content of 8.3 wt%?

2) How much radiogenic ⁴⁰Ar* are contained in these 10 mg K-feldspar if its age is ~350 Ma? Provide the amount in both, moles and volume, the latter in ml_STP.

Additional information: Atomic weights: ⁴⁰Ar=39.962 amu, ⁴⁰K=39.964 amu (note: amu = grams/mol). Molar volume at standard temperature and pressure (STP: 273.15 K and 1 bar): 22.71 liter. This means that 1 mol of any gas has a volume of 22.71 litres at STP, independent of the type of gas (its just the mass that varies!).

Provide the answer as a PDF if solved using Excel, or as a scan if solved by hand. Not only provide the result, but also the way you did the calculation!

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