A student is given a crucible and asked to determine wheather it is made of pure
ID: 914032 • Letter: A
Question
A student is given a crucible and asked to determine wheather it is made of pure platinum. The student first weighs the crucible in air and then weighs it suspended in water (density equals 0.9986 g/mL). The readings are 860.2 g and 820.2 g, respectively. Based on these measurements and given that the density of platinum is 21.45 g/cm3 , what should the students conclusion be? (hint: an object suspended in a fluid is buoyed yp the mass of the fluid displaced by the object, neglect the bouyancy of air).
please show work
Explanation / Answer
Given,
Weight in air (Wair) = 820.2 gms
Weight in water (Wwater) = 860.2 gms
Weight of water of equal volume(as compared to air) = Wwater - Wair = 860.2 - 820.2 = 40 gms
Weight of the crucible = 40 gms
Density = Mass/Volume
Volume = Mass/Density = 40/0.9986 = 40.06 cm^3
Crucible density = 860.2/40.06 = 21.47 gm/cm^3
But the actual density of platinum is 21.45 gm/cm^3, hence it is not pure platinum
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