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Ch.3 - Mass Relationships in Chemical Reactions
Chapter 3, Problem 71b

An alternative method for producing hydriodic acid is the reaction of iodine with hydrogen sulfide:H2S + I2 → 2 HI + S (b) How many grams of HI are produced from the reaction of 95.4 g of H2S with excess I2?

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1
Identify the balanced chemical equation: \( \text{H}_2\text{S} + \text{I}_2 \rightarrow 2 \text{HI} + \text{S} \).
Calculate the molar mass of \( \text{H}_2\text{S} \) using the atomic masses of hydrogen and sulfur.
Determine the number of moles of \( \text{H}_2\text{S} \) by dividing the given mass (95.4 g) by its molar mass.
Use the stoichiometry of the balanced equation to find the moles of \( \text{HI} \) produced. According to the equation, 1 mole of \( \text{H}_2\text{S} \) produces 2 moles of \( \text{HI} \).
Calculate the mass of \( \text{HI} \) produced by multiplying the moles of \( \text{HI} \) by its molar mass.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It allows chemists to determine the amount of substances consumed and produced in a reaction. In this case, understanding the stoichiometric coefficients from the balanced equation is essential to calculate how many grams of HI can be produced from a given mass of H2S.
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Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is crucial for converting between grams and moles, which is necessary for stoichiometric calculations. For this problem, calculating the molar mass of H2S and HI will enable the conversion of the mass of H2S into moles, facilitating the determination of the mass of HI produced.
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Limiting Reactant

The limiting reactant is the substance that is completely consumed first in a chemical reaction, thus determining the maximum amount of product that can be formed. In this scenario, since I2 is in excess, H2S is the limiting reactant. Identifying the limiting reactant is essential for accurately calculating the yield of HI produced from the reaction.
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