When exposed to sulfur in the air, silver forms a dark layer of silver sulfide $\left(\mathrm{Ag}_{2} \mathrm{~S}\right)$ known as "tarnish." To remove this tarnish, an aluminum-based cleaning solution may be used. The aluminum reacts with the silver sulfide and converts it back to pure silver:
$$
3 \mathrm{Ag}_{2} \mathrm{~S}+2 \mathrm{Al} \rightarrow 6 \mathrm{Ag}+\mathrm{Al}_{2} \mathrm{~S}_{3}
$$

Removing silver tarnish with aluminum foil
What is the minimum mass of $\mathrm{Al}$ needed to completely react with 1.45 grams of $\mathrm{Ag}_{2} \mathrm{~S}$ ?

Show molar masses of reactants and products
Choose 1 answer:
(A) $0.105 \mathrm{~g}$
(B) $0.237 \mathrm{~g}$
(c) $0.695 \mathrm{~g}$

Question

When exposed to sulfur in the air, silver forms a dark layer of silver sulfide $\left(\mathrm{Ag}_{2} \mathrm{~S}\right)$ known as "tarnish." To remove this tarnish, an aluminum-based cleaning solution may be used. The aluminum reacts with the silver sulfide and converts it back to pure silver:
$$
3 \mathrm{Ag}_{2} \mathrm{~S}+2 \mathrm{Al} \rightarrow 6 \mathrm{Ag}+\mathrm{Al}_{2} \mathrm{~S}_{3}
$$

Removing silver tarnish with aluminum foil
What is the minimum mass of $\mathrm{Al}$ needed to completely react with 1.45 grams of $\mathrm{Ag}_{2} \mathrm{~S}$ ?

Show molar masses of reactants and products
Choose 1 answer:
(A) $0.105 \mathrm{~g}$
(B) $0.237 \mathrm{~g}$
(c) $0.695 \mathrm{~g}$

Accepted Answer

***B*** ∻Key Concept∻ ⚹Stoichiometry⚹ ∻Explanation∻ ⚹To find the minimum mass of aluminum needed, we use stoichiometry. First, calculate the moles of $Ag_2S$ using its molar mass, then use the balanced chemical equation to find the moles of $Al$ required, and finally convert this to grams using the molar mass of $Al$.⚹◊What is the molar mass of $Al_{2}S_{3}$?⍭ Generate me a similar question◊

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