# Chemistry

posted by on .

To extract gold from its ore, the ore is treated with sodium cyanide solution in the presence of oxygen and water.
4 Au(s) + 8 NaCN(aq) + O2(g) + 2 H2O(l) -> 4 NaAu(CN)2(aq) + 4 NaOH(aq)

• Chemistry - ,

What are you asking for? To balance the equation

• Chemistry - ,

oh...sorry
a)Determine the mass of gold that can be extracted if 27.1 g sodium cyanide is used.

and

b)If the mass of the ore from which the gold was extracted is 126.5 g, what percentage of the ore is gold?

• Chemistry - ,

4 NaAu(CN)2(aq), this is the gold, right? But is the 2 on the bottom of Au such as Au2.

• Chemistry - ,

i'm not really sure. i got this problem to solve, but i couldn't figure it out -_-'

there's no 2 on the bottom of Au

• Chemistry - ,

1. Write the equation and balance it.
2. Convert 27.1 g NaCN to moles. moles = grams/molar mass.
3. Using the coefficients in the balanced equation, convert moles NaCN to moles Au.
4. Now convert moles Au to grams Au. grams = moles Au x molar mass Au.
This gives you the theoretical yield of Au possible.

For percent. % Au in the ore =
(grams ore extracted/theoretical yield)*100 = ??
Post your work if you get stuck.

• Chemistry - ,

is this the right answer for mass of gold extracted then : 77.0 g ??
and 164.3 % percent yield??

• Chemistry - ,

No, I don't get those answers. Something more like 55 g Au (that's just a close number) and something like 43% Au in the ore.Check those numbers. If you want to post your work I'll be glad to check it for you.

• Chemistry - ,

well my question is the same as amy's but mine says:
Determine the mass of gold that can be extracted if 24.7 g sodium cyanide is used.
and
If the mass of the ore from which the gold was extracted is 129.5 g, what percentage of the ore is gold?
but i tried her numbers. could you Please work this out for me for future reference, I"m completely confused here.

• Chemistry - ,

also for percent yield i thought it was (actual results)/(theoretical results) X 100, so wouldnt it be 126.5g/ 55g=230??

• Chemistry - ,

c -- Please don't piggy-back on another's question.

• Chemistry - ,

okk sorry amy.

ps: ive never used this before ms. sue, so don't be rude.

• Chemistry--To c - ,

For the new numbers you quoted, I get 49.6 g Au possible with percent Au =
(49.6/126.5) *100 = ??
For percent, in this case, you are asking for percent gold in the 126.5 grams sample of ore, not percent yield. The percent figure obtained assumes the yield of the chemical process is 100%. If you will re-post your question, as Ms Sue suggests, and post your work, I shall be glad to check it for errors. In the mean time,check my arithmetic also.

• Chemistry - ,

Too many posts make errors possible. I just noticed that c had ore mass of 129.5 so replace the 126.5 g with 129.5 g for the question by c.

As for Ms Sue's response, it isn't rude; it's telling you that piggy-backed questions often get overlooked and/or are not answered. It's so confusing trying to answer two questions under the same "title".

• Metalurgy - ,

If a Tonne of gold ore is said to have a gold concentration of 8% gold, how do you estimate the number of grams yield per Tonne of ore?
And what's the yield of gold per tonne ore