High School

The compositions in atom% of an alloy that consists of 97 wt% Al and 3 wt% Cu are:

Select one:

a. 99.7 at% Al and 0.3 at% Cu

b. 95.7 at% Al and 4.3 at% Cu

c. 89.7 at% Al and 10.3 at% Cu

d. 98.7 at% Al and 1.3 at% Cu

e. 97.8 at% Al and 2.2 at% Cu

Answer :

The composition in atom% of the alloy consisting of 97% wt% Al and 3% wt% Cu is 95.7 at% Al and 4.3 at% Cu (option b).

An alloy consists of two or more metals or a metal and a non-metal. In this case, the alloy is made up of 97% wt% Aluminum (Al) and 3 wt% Copper (Cu).

To find the compositions in atom% of the alloy, we need to convert the weight percent to atomic percent. First, we need to calculate the moles of Al and Cu using their atomic weights and the given weight percentages.

Moles of Al = (Weight percent of Al / Atomic weight of Al) * Total weight of the alloy

= (97 / 26.98) * Total weight of the alloy

Moles of Cu = (Weight percent of Cu / Atomic weight of Cu) * Total weight of the alloy

= (3 / 63.55) * Total weight of the alloy

Then, we can calculate the atomic percent of Al and Cu by dividing the moles of each element by the total moles of the alloy and multiplying by 100.

Atomic percent of Al = (Moles of Al / Total moles of the alloy) * 100

Atomic percent of Cu = (Moles of Cu / Total moles of the alloy) * 100

Using the given weight percentages and the atomic weights of Al and Cu, we can calculate the atomic percent compositions of the alloy to be 95.7 at% Al and 4.3 at% Cu. Therefore, the correct answer is option b. 95.7 at% Al & 4.3 at% Cu.

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