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Question

Jacy bought a gold necklace weighing 21.3 grams from a flea market. She filled a 10mL graduated cylinder with water to the 5.0mL mark and dropped her necklace in. The level in the graduated cylinder rose to 7.4mL. Is her necklace real or fake? If not, identify the link possible composition of her necklace.

gold: 19.3 g/cm3

copper: 8.86 g/cm3

bronze: 9.87 g/cm3

Answer 1

21.3/2.4 = 8.875 g/ml. Pure gold (24 karat) is 19.32 g/ml.

8.875/19.32 = 45.94% gold.

45.94% x 24k = 11.02k gold.

Since it is unlikely that copper or another metal or alloy would be visually mistaken for gold (unless it was gold-plated), this chain is probably 11k gold alloy.

Answer 2

Density is mass/volume/ In this case the volume is the displacement of the water which is 2.4 mL. So, D=21.3/2.4 = 8,88 g/mL. This looks like copper if it is a [ure substance.