A.) Consider a piece of gold jewelry that weighs 9.40 g and has a volume of 0.65

Question

A.) Consider a piece of gold jewelry that weighs 9.40 g and has a volume of 0.650 cm3 . The jewelry contains only gold and silver, which have densities of 19.3 g/cm3 and 10.5 g/cm3, respectively. If the total volume of the jewelry is the sum of the volumes of the gold and silver that it contains, calculate the percentage of gold (by mass) in the jewelry.

B.)The relative amount of gold in an alloy is commonly expressed in units of karats. Pure gold is 24-karat, and the percentage of gold in an alloy is given as a percentage of this value. For example, an alloy that is 50% gold is 12-karat. State the purity of the gold jewelry in karat.

Explanation / Answer

ans)

a)

from above data taht

total mass = 9.40 g

let mass of gold = x g

so mass of silver = (9.40-x) g

vol of gold = x / 19.3

vol of silver = (9.40-x) /10.5

total vol = x/19.3 + (9.40-x) /10.5 = 0.650

=> -8.8x=-49.6975

=> x = 5.65 g

so % of gold = 5.65*100/9.40= 60.10%

part b

pure gold - 24 karat - 100%

100 % --- 24 karat

60.1%by mass=24 karat/00%*60.1%

60.1%by mass=14.424 karat

the purity of gold is 14.4 karats

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