Question

My grandmother left me some silver years ago. I opened the box containing the silver and it had tarnished. Using the equation below, if I had 300 g of silver that had tarnished and 175g H2S, which would be the limiting reactant?

Answer 1

Silver Ag will be the limiting reagent.

Step-by-step explanation:

The balanced reaction is:

2 Ag(s) + H₂S(g) ⇒ Ag₂S(s) + H₂(g)

By reaction stoichiometry (that is, the relationship between the amount of reagents and products in a chemical reaction), the following amounts of reactant and product participate in the reaction:

• Ag: 2 moles
• H₂S: 1 mole
• Ag₂S: 1 mole
• H₂: 1 mole

Being:

• Ag: 107.87 g/mole
• H: 1 g/mole
• S: 32 g/mole

the molar mass of the compounds participating in the reaction is:

• Ag: 107.87 g/mole
• H₂S: 2*1 g/mole + 32 g/mole= 34 g/mole
• Ag₂S: 2*107.87 g/mole + 32 g/mole= 247.74 g/mole
• H₂: 2* 1 g/mole= 2 g/mole

Then, by reaction stoichiometry, the following mass quantities of each compound participate:

• Ag: 2 mole* 107.87 g/mole= 215.74 g
• H₂S: 1 mole* 34 g/mole= 34 g
• Ag₂S: 1 mole* 247.74 g/mole= 247.74 g
• H₂: 2* 1 mole* 2 g/mole= 2 g

If you have 175g of H₂S, you can apply the following rule of three: if by stoichiomatry 34 grams of H₂S react with 215.74 grams of Ag, 175 grams of H₂S with how much mass of Ag does it react?

`mass of Ag=(175 grams of H_(2)S* 215.74 grams of Ag)/(34 grams of H_(2)S)`

mass of Ag= 1,110.43 grams

But 1,110.43 grams of Ag are not available, 300 gra s are available. Since you have less mass than you need to react with 175 grams of H₂S, silver Ag will be the limiting reagent.