Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Helphelp on December 31, 2019, 10:16:07 AM
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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!
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Calculate the Mole of silverchloride. This correspond to the silver. Calculate the mass of silver. Then compare to the mass of the coin.
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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%
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@MNIO
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