Problem 103 - A Complete Resource Book in Chemistry for JEE Main

Question

One mole of fluorine is reacted with two mole of hot and concentrated KOH. The products formed are \(\mathrm{KF}, \mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{O}_{2} .\) The molar ratio of \(\mathrm{KF}, \mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{O}_{2}\) respectively is (a) \(1: 2: 1\) (b) \(1: 2: 2\) (c) \(0.5: 1: 2\) (d) \(2: 1: 0.5\)

Step-by-Step Solution

Answer

The molar ratio is \(2:1:0.5\) (option d).

Step 1: Write the balanced chemical equation

The chemical reaction between fluorine (F₂) and potassium hydroxide (KOH) is described by:\[\mathrm{2F}_{2} + 4\mathrm{KOH} \rightarrow \mathrm{4KF} + 2\mathrm{H}_{2}\mathrm{O} + \mathrm{O}_{2}\]This balanced equation shows the reaction of fluorine and potassium hydroxide to form potassium fluoride, water, and oxygen.

Step 2: Determine mole ratios from the equation

From the balanced equation:- 2 moles of \(\mathrm{F}_{2}\) react with 4 moles of \(\mathrm{KOH}\) to produce 4 moles of \(\mathrm{KF}\), 2 moles of \(\mathrm{H}_{2}\mathrm{O}\), and 1 mole of \(\mathrm{O}_{2}\).

Step 3: Calculate the molar ratio for the given scenario

According to the problem, 1 mole of \(\mathrm{F}_{2}\) is reacted with 2 moles of \(\mathrm{KOH}\). Since the equation provides a ratio of 2 \(\mathrm{F}_{2}\) to 4 \(\mathrm{KOH}\), this is equivalent to 1 \(\mathrm{F}_{2}\) to 2 \(\mathrm{KOH}\). From this condition, the product formation will also be halved:- 2 moles of \(\mathrm{KF}\) (from halving 4 moles)- 1 mole of \(\mathrm{H}_{2}\mathrm{O}\) (from halving 2 moles)- 0.5 mole of \(\mathrm{O}_{2}\) (from halving 1 mole).

Step 4: Identify the molar ratio of the products

The balanced reaction indicates that 1 mole of \(\mathrm{F}_{2}\) produces 2 moles of \(\mathrm{KF}\), 1 mole of \(\mathrm{H}_{2}\mathrm{O}\), and 0.5 mole of \(\mathrm{O}_{2}\) under the reacted condition. Hence, the molar ratio of the products \(\mathrm{KF}, \mathrm{H}_{2}\mathrm{O}, \mathrm{O}_{2}\) for 1 mole of fluorine is 2:1:0.5.

Key Concepts

Chemical Reactions

Chemical reactions occur when substances, known as reactants, transform into new substances, called products. In the given scenario, we have fluorine \( (\text{F}_2) \) and potassium hydroxide \( (\text{KOH}) \) as our reactants. When they react, they form new substances: potassium fluoride \( (\text{KF}) \), water \( (\text{H}_2\text{O}) \), and oxygen \( (\text{O}_2) \). This transformation shows the fundamental nature of chemical reactions. Understanding this, we realize that the starting materials are entirely different from what we end up with. This transformation involves breaking and forming chemical bonds and is described by a chemical equation. Let's summarize the key points of chemical reactions:

• They involve reactants turning into products.
• Atoms are conserved but rearranged in new ways.
• They are represented through chemical equations that provide a snapshot of the reaction path.
• The balancing of these equations is critical to show that mass is conserved (more on balancing later).

Whether a reaction is simple or complex, these principles hold true, making chemical reactions a foundational element in chemistry.

Mole Concept

The mole concept is a core principle in chemistry that lets us quantify the amount of substance. It allows chemists to count particles like atoms and molecules by weighing them. One mole is \( 6.022 \times 10^{23} \) particles, known as Avogadro's number. In the exercise, we're told that one mole of fluorine reacts with two moles of potassium hydroxide. Understanding this through the mole concept shows us how these quantities translate into the balanced chemical equation. Key ideas of the mole concept include:

• Crucially connects macroscopic observations (like weighing compounds) to the microscopic world of atoms and molecules.
• Facilitates a straight conversion to mass by multiplying moles by the substance's molar mass.
• Allows stoichiometric calculations in reactions to easily determine how much of each reactant or product is involved.

Ensuring you've got strong grip on the mole concept is essential as it lets you understand how chemists measure and react compounds precisely.

Balanced Equation

A balanced equation ensures that the same number of each type of atom appears on both sides of a chemical reaction. This follows the Law of Conservation of Mass which states that mass cannot be created or destroyed. In this exercise, the balanced equation is:\[\text{2F}_2 + \text{4KOH} \rightarrow \text{4KF} + \text{2H}_2\text{O} + \text{O}_2\]This equation shows that on both sides we have:

• 4 fluorine atoms.
• 4 potassium atoms from the KOH molecules.
• 4 oxygen atoms (one from the \(\text{O}_2\) and the rest from \(\text{KOH}\) and \(\text{H}_2\text{O}\)).
• 4 hydrogen atoms from the \(\text{H}_2\text{O}\) molecules.

The math of balancing ensures no atoms disappear or are added, maintaining the same number of each type throughout the reaction.Here are essential pointers about balancing equations:

• It's a method to visually verify that mass is conserved in a chemical reaction.
• Coefficients (the numbers in front of molecules in the equation) are adjusted to ensure atoms are balanced.
• Balanced equations are vital for accurate stoichiometry calculations, which allow us to derive correct reactant and product ratios.

Mastering the skill of balancing equations is a fundamental step for solving more complex chemical problems.