Gold is alloyed(mixed) with other metals to increase its hardness in making jewelry. (a) consider a piece of gold jewelry that weighs 9.85 g and has a volume of 0.675 cm3. the jewelry contains only gold and silver, which have densities of 19.3 g/cm3 and 10.5 g/cm3, repectively. 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.

The percentage of gold(by mass) in the jewelry is 61.52%.

Explanation:

Mass of the jewelry ,M= 9.85 g

Mass of the gold in jewelry =

Mass of the silver in jewelry =

Volume of the jewelry =

Volume of the gold in jewelry =

Density of gold

Volume of the silver in jewelry =

Density of gold

..(1)

..(2)

On solving equation (1)and(2) we get:

and after that values of

The percentage of gold(by mass) in the jewelry:

The percentage of gold(by mass) in the jewelry is 61.52%.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.