density question set up

Chemistry
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sylvanite is a mineral that contains 28.0% gold by mass. When 171 grams of sylvanite is added to a graduated cylinder contains 155 mL of water, the water level in the cylinder rose to 205mL. By how many milliliters did the gold increase the volume of water?".

Sep 30th, 2015

Thank you for the opportunity to help you with your question!

Sylvanite is 28.0% gold = 28 g out of 100 g is gold

28 / 100 = x / 171

171 g of Sylvanite contains 47.88 g of gold

Water displacement: 155 mL to 205 mL = + 50 mL

171 g Sylvanite displaces 50 mL H2O

If I understand this correctly, the Q is how much displacement due to the gold content only

Well, that would be 28.0% of the total displacement, i.e.

(50 mL)(.28) = 14 mL H2O displaced due to gold content alone

Or you could take the roundabout way, as in

X / 50 = 47.88 / 171  x = 14


Please let me know if you need any clarification. I'm always happy to answer your questions.
Sep 30th, 2015
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My text states the density of gold is 19.3 g/mL. So would I have to divide the 171 grams of sylvanite by the gold density first? 

Sep 30th, 2015

That is the density of gold, yes. However, the question above asks how much water was displaced due to the gold content in the Sylvanite. The answer is 14 mL (28%) out of the 50 mL was displaced due to the gold content. I'm not clear on where density comes into the game. Is there a second part to this question?

Sep 30th, 2015
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The entire question reads:

sylvanite is a mineral that contains 28.0% gold by mass. When 171 grams of sylvanite is added to a graduated cylinder containing 155 mL of water, the water level in the cylinder rose to 205mL. By how many milliliters did the gold increase the volume of water?" See attached density table... 

Sylvanite does not appear on density table only gold with a value of 19.3g/mL. table2.9.pdf 

Im guessing added information to confuse me? below is what i did with the problem to solve. I'm pretty sure I am way off.

question 4.pdf 

Sep 30th, 2015

let's see...

50 mL displaced by 171 g of mixed compound (47.88 g gold + 123.12 g unknown)

gold: 19.3 g/mL = 47.88 g / x mL  --> 2.48 mL displaced due to the gold content

leaves 123.12 g / 47.52 mL = 2.59 g/mL     glass has a density of 2.6 g/mL

that may be your mystery compound

in my first answer I assumed equal density, that's how I came up with 14 mL

since they stretch 'mixed compound' and the density of gold... we assume different densities, ergo, see above

  

Sep 30th, 2015

actually, I went diggin':

Sylvanite: AgAuTe4, Silver Gold Telluride, three different densities involved...

Sep 30th, 2015

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