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Topic: percentage mass of gold in an alloy  (Read 4023 times)

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Zamzen

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percentage mass of gold in an alloy
« on: February 12, 2011, 07:05:54 AM »
Question is, what is the percentage mass of gold in an alloy that contains gold and silver only. Density of gold is 19,3g/cm^3 and of silver is 10.5g/cm^3. The volume of the alloy is 0.675cm^3 and the mass is 9.85g. And the volume of the alloy is the sum of the volume of the gold and the silver.

I get stuck pretty quickly, I am thinking about isolating the mass of the gold but i cant find the solution.
density of alloy = 9,85/0.675 = 14.6g/cm^3. Also i Know that x19.3 + y10.5 = 14.6. And that
14.6 = (mass gold + mass silver) / 0.675.

The answer is 60.6% but i don't see a way to get there. Thankful for any help that i can get.

opti384

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Re: percentage mass of gold in an alloy
« Reply #1 on: February 12, 2011, 07:12:15 AM »
Well how about setting the volume of gold as X and the volume of silver as Y. I think you could derive two equations from there.

Zamzen

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Re: percentage mass of gold in an alloy
« Reply #2 on: February 12, 2011, 07:26:46 AM »
Well how about setting the volume of gold as X and the volume of silver as Y. I think you could derive two equations from there.

Cool, thanks.

Borek

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Re: percentage mass of gold in an alloy
« Reply #3 on: February 12, 2011, 08:23:50 AM »
And the volume of the alloy is the sum of the volume of the gold and the silver.

Follow opti suggestion, but be aware of the fact that above assumption is in general wrong - volumes are not additive.
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