Hello -

This is actually my sisters homework problem (junior in highschool)- she spent time trying to figure it out and her teacher gave her some formulas to help her out. She finally asked big sister for help, and I have no clue where to start for this! I've been working on it for over an hour. Here's the prob:

Gold and silver alloy weighs 9.85g, has a volume of 0.675cm3. Gold has a density of 19.39g/cm3 and silver 10.5g/cm3. Calculate the percentage of Gold in grams that is contained in the alloy.

Her teacher gave her the following formulas:

9.85g = x(g) + y(g)

0.675cm3 = x(1cm3/19.3g) = y(1cm3/10.5g)

We easily figured out the density of the alloy = 14.59 g/cm3, but we have no idea where to go next. Could you give us a few ideas to help us along? Thank you so much!

Thanks,

Melissa

I'll give it a shot here

the mass of the alloy is 9.85 g

this mass is made up of the mass of gold and the mass of silver so we have

mass

_{alloy}= mass_{gold}+ mass_{silver}9.85 g = mass

_{gold}+ mass_{silver}then mass

_{silver}= 9.85 g - mass_{gold}density of alloy = mass

_{alloy}/ volume_{alloy}= (mass_{gold}+ mass_{silver}) / volume_{alloy}density of alloy = (mass

_{gold}+ mass_{silver}) / volume_{alloy}= (mass

_{gold}+ (9.85 g - mass_{gold})) / volume_{alloy}solving this should give you the mass of gold

divide by the original amount and multiply by 100

The book shows the answer as 61.5% gold by mass. I can't get there with these formulas. What am I doing wrong?

Chemistry Tutor wrote:Fantastic! Thanks!