Question

Hi! I'm having trouble solving this question, not sure how to go about starting it:

Magnalium is a solid mixture of aluminum metal & magnesium metal. An irregular shaped chunk of a sample of magnalium is weighed twice, once in air (211.5g) and once in vegetable oil (135.3g) by using a spring scale. If the densities of pure aluminum, pure magnesium, & vegetable oil are 2.70g/cm^3, 1.74g/cm^3, and 0.926g/cm^3, respectively, then what is the mass percent of magnesium in the chunk of magnalium? Assume that the density of a mixture of the two metals is a linear function of the mass percent composition.

Thanks.

Answer 1

you know mass (same as in air)
find volume from density of oil
densityoil*volume=difference in masses air vs oil.

Now, density=mass/volume

then you have a linear equation
DensityMagnesium*volumetotal*PercentMg + DensityAl*volumetotal*(1-percentMg)=massblock

solve for percentMg, then you have percentAl (percents are in decimal form)