Problem 13 - Chemistry in 30 days

Question

In the following reaction $$ 2 \mathrm{H}_{2} \mathrm{~S}+\mathrm{SO}_{2} \rightarrow 2 \mathrm{H}_{2} \mathrm{O}+3 \mathrm{~S} $$ 1\. mol each of \(\mathrm{SO}_{2}\) and \(\mathrm{H}_{2} \mathrm{~S}\) will give sulphur (a) \(1 \mathrm{~mol}\) (b) \(3 \mathrm{~mol}\) (c) \(1.5 \mathrm{~mol}\) (d) \(2 \mathrm{~mol}\)

Step-by-Step Solution

Answer

The reaction will give 1.5 mol of sulfur.

Step 1: Understanding the Reaction

The chemical reaction given is \( 2 \mathrm{H}_{2} \mathrm{~S} + \mathrm{SO}_{2} \rightarrow 2 \mathrm{H}_{2} \mathrm{O} + 3 \mathrm{~S} \). Here, \(2\) moles of \(\mathrm{H}_{2} \mathrm{~S}\) react with \(1\) mole of \(\mathrm{SO}_{2}\) to produce \(3\) moles of sulfur (\(\mathrm{S}\)).

Step 2: Determining the Limiting Reactant

We need to determine which reactant limits the amount of sulfur produced. According to the balanced reaction, \(2\) moles of \(\mathrm{H}_{2} \mathrm{~S}\) are required for every \(1\) mole of \(\mathrm{SO}_{2}\). Here, we have \(1\) mole of each, thus \(\mathrm{H}_{2} \mathrm{~S}\) is the limiting reactant since it doesn't provide enough to fully react with \(\mathrm{SO}_{2}\).

Step 3: Calculating Sulfur Production

Considering \(\mathrm{H}_{2} \mathrm{~S}\) as the limiting reactant, we have \(1\) mole of it. Based on the balanced equation, \(2\) moles of \(\mathrm{H}_{2} \mathrm{~S}\) produce \(3\) moles of \(\mathrm{S}\). Therefore, \(1\) mole of \(\mathrm{H}_{2} \mathrm{~S}\) will produce \(\frac{3}{2} = 1.5\) moles of sulfur.

Key Concepts

Limiting Reactant

In any chemical reaction, the limiting reactant is the substance that is entirely consumed first, limiting the amount of product formed. It determines the maximum mass of product that can be produced from given reactants. Here's a simple way to identify the limiting reactant:

• Compare the mole ratio of the reactants available with the mole ratio in the balanced chemical equation.
• The reactant that has a lesser amount according to the required ratio is the limiting reactant.

In our exercise, we have 1 mole of each reactant: \( \mathrm{SO}_{2} \) and \( \mathrm{H}_{2} \mathrm{~S} \). The balanced equation shows that 2 moles of \( \mathrm{H}_{2} \mathrm{~S} \) are needed for every 1 mole of \( \mathrm{SO}_{2} \). Thus, \( \mathrm{H}_{2} \mathrm{~S} \) is the limiting reactant, as we only have half the moles needed to react with all the \( \mathrm{SO}_{2} \). So, the amount of sulfur produced is limited by \( \mathrm{H}_{2} \mathrm{~S} \).

Chemical Equations

Chemical equations are symbolic representations of chemical reactions. They consist of the reactants (starting materials) on the left side and the products (substances formed) on the right, separated by an arrow pointing from left to right.

• Reactants and products are written as chemical formulas.
• Coefficients are used to balance the equation, ensuring the law of conservation of mass is upheld. This means the same number of each type of atom appears on both sides of the equation.

In our exercise:

• \( 2 \mathrm{H}_{2} \mathrm{~S} \) and \( \mathrm{SO}_{2} \) are the reactants.
• \( 2 \mathrm{H}_{2} \mathrm{O} \) and \( 3 \mathrm{~S} \) are the products.
• The equation is balanced as the number of hydrogen, sulfur, and oxygen atoms are equal on both sides.

This balanced equation lets us understand the specific quantities of reactants needed and products formed, vital for stoichiometric calculations.

Mole Concept

The mole concept is a fundamental aspect of stoichiometry, which is the calculation of reactants and products in chemical reactions. A mole is a unit that measures the amount of substance. One mole contains \( 6.022 \times 10^{23} \) entities (Avogadro's number), be it atoms, molecules, ions, or other particles. In the realm of chemistry:

• This concept allows chemists to count particles by weighing them, as it correlates the macroscopic scale to the submicroscopic world.
• It ties the mass of a substance to the number of entities, enabling conversions between grams and moles using molar mass (grams per mole).

In the given chemical reaction, knowing the moles of \( \mathrm{H}_{2} \mathrm{~S} \) and \( \mathrm{SO}_{2} \) allows us to calculate the number of moles of \( \mathrm{S} \) that can be produced. We determine that 1 mole of \( \mathrm{H}_{2} \mathrm{~S} \) will produce 1.5 moles of sulfur based on the ratio derived from the balanced equation.