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Topic: A possibly difficult stoichiometry problem...  (Read 1090 times)

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Offline Helphelp

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A possibly difficult stoichiometry problem...
« on: December 31, 2019, 10:16:07 AM »
A coin made of silver with a mass of 5.82 grams is dissolved by reacting with HNO3. When we add NaCl to the solution, a silver salt precipitates and has a mass of 7.20 grams. Determine the percentage of silver in the coin.

The answer is supposed to be 93,1% ...But I don't really know how to solve this problem, for now I figured that the reaction's equation is:
2Ag(s) + 2HNO3(l)+2NaCl(s)→ 2AgCl(s) + 2NaNO3(l) +H2(g)...but I might be wrong!

Offline chenbeier

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Re: A possibly difficult stoichiometry problem...
« Reply #1 on: December 31, 2019, 11:13:28 AM »
Calculate the Mole of silverchloride. This correspond to the silver. Calculate the mass of silver. Then compare to the mass of the coin.

Offline MNIO

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Re: A possibly difficult stoichiometry problem...
« Reply #2 on: January 01, 2020, 01:48:40 PM »
you could use the typical problem solving process for stoichiometry calcs
  (1) write a balanced equation
  (2) convert everything to moles
  (3) determine limiting reagent
  (4) convert moles limiting reagent to moles products (or whatever else you're interested in)
  (5) convert moles back to mass.. this is theoretical mass
  (6) % yield (if needed) = (actual mass recovered / theoretical mass) * 100%
the usual steps

however... this is such a simple problem, we could just use that dimensional analysis (factor label) method you've been learning like this

  7.20g AgCl        107.9g Ag
 -------------- x ----------------- x 100% =93.15% Ag in the coin
  5.82g coin       143.32g AgCl

which I would report to 3 sig figs as 93.2%

Offline billnotgatez

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Re: A possibly difficult stoichiometry problem...
« Reply #3 on: January 03, 2020, 03:08:36 PM »
@MNIO
Could you confirm that you have read the forum rules?
See the link center page above (in red).
No recriminations, just a question to make sure we are all on the same page.

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