Answer :
The compositions in atom% of an alloy consisting of 97 wt% Al and 3 wt% Cu are approximately 97.8 at% Al and 2.2 at% Cu. This calculation uses the atomic weights of Al and Cu to convert from wt% to at%.
The composition of an alloy using atom percent (at%) is different from weight percent (wt%) because the at% considers the number of atoms of each element, while the wt% considers the weight. To determine the at% of Al (Aluminium) and Cu (Copper), we need to know the atomic weights of Al and Cu to convert wt% to at%.
The atomic weight of Al is approximately 26.98 g/mol and for Cu is 63.55 g/mol. Using these values, the fraction of Al is 97/(26.98) and for Cu is 3/(63.55). Normalize these values to get the at%. The result should be around 97.8 at% Al and 2.2 at% Cu, making option d the correct answer.
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