Question

2. A piece of jewelry was tested by method A (Density of Irregularly Shaped Solids by Water Displacement) to determine if it was pure silver or a silver-plated resin. The mass of the jewelry was 1.52 g. A chemist measured the volume displaced by the item, then repeated the experiment. She obtained two different values, 0.16 mL and 0.14 mL. Calculate the density of this item using each volume amount. How do the experimentally obtained density values compare to that of pure silver? If we assume that the sample really was pure silver, how accurate and precise were the chemist's results?

Answer 1

Mass of jewellery=1.52g

Volume of jewellery in trial 1= 0.16ml

Density= mass÷volume

Density of jewellery in trial 1= 1.52g÷0.16ml = 9.5g/ml

Volume of jewellery in trial 2= 0.14g

Density of jewellery in trial 2= 1.52g÷0.14ml = 10.86g/ml

Density of pure silver= 10.5g/ml

So we can say trial 2 was really accurate to calculate the density of the jewellery and I think the jewellery is authentic silver.

Deviation of experiment is

Trial 1= 9.5-10.5 = -1.0g/ml

Trial 2= 10.86-10.5= 0.36g/ml

Average deviation= (-1.0+0.36)÷2 = -0.32g/ml

Percent deviation= (0.32÷10.5)×100= 3.05%

As we can see the deviation from pure silver is very low and thus the results can be considered very accurate and the jewellery can be deemed pure silver.