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Chapter 8: Problem 21

Write an equation for the reaction of potassium metal with water.

Short Answer

Expert verified
2K + 2H_2O -> 2KOH + H_2.

Step by step solution

01

Identify Reactants

When potassium (K) reacts with water ( ext{H}_2 ext{O} ), the elements involved are potassium and water. Here, water acts as a solvent and reactant, while potassium is a metal that participates actively in the reaction.
02

Write Chemical Equation Structure

The general reaction of an alkali metal such as potassium with water involves the formation of a hydroxide and hydrogen gas. Thus, the products of this reaction will be potassium hydroxide (KOH) in aqueous form and hydrogen gas ( ext{H}_2 ).
03

Balance the Equation

The unbalanced equation is K + ext{H}_2 ext{O} ightarrow ext{KOH} + ext{H}_2 . To balance it, ensure the number of each type of atom is equal on both sides. Adjust by placing coefficients before the compounds: 2K + 2 ext{H}_2 ext{O} ightarrow 2 ext{KOH} + ext{H}_2 , resulting in a balanced equation.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Chemical Reactions
A chemical reaction involves the transformation of one or more substances into different substances. In the case of potassium reacting with water, we see a fundamental example of a chemical reaction. When potassium metal comes into contact with water, it undergoes a chemical transformation that results in the formation of new substances: potassium hydroxide and hydrogen gas. During this process:
  • Bonds between atoms in the reactants (potassium and water) break.
  • New bonds form to create the products.
This transformation changes the physical and chemical properties of the substances involved, emphasizing the creative power of chemical reactions.
Balancing Chemical Equations
Balancing chemical equations is crucial to accurately represent a chemical reaction. It ensures that the law of conservation of mass is followed, indicating that matter is neither created nor destroyed in a chemical reaction. For the reaction of potassium with water:
  • The unbalanced chemical equation is: \[ K + \text{H}_2\text{O} \rightarrow \text{KOH} + \text{H}_2 \]
  • To balance this, equalize the number of each type of atom on both sides of the equation.
  • The balanced equation becomes: \[ 2K + 2\text{H}_2\text{O} \rightarrow 2\text{KOH} + \text{H}_2 \]
This balanced equation correctly represents the equality of each atom type, reflecting the true stoichiometry of the reaction.
Alkali Metals
Alkali metals are a group of elements located in Group 1 of the periodic table. They include lithium, sodium, potassium, rubidium, cesium, and francium. These elements are known for their high reactivity, especially with water. Important characteristics of alkali metals include:
  • They have one electron in their outermost shell, making them highly reactive.
  • They tend to form hydroxides when reacting with water.
  • Alkali metals are soft and can be cut with a knife.
When potassium, an alkali metal, reacts with water, it does so vigorously and often produces enough heat to ignite the liberated hydrogen gas, demonstrating the characteristic reactivity of this group.
Hydroxide Formation
Hydroxide formation is a common result when alkali metals react with water. In the reaction between potassium and water, one of the primary products is potassium hydroxide (KOH). Here鈥檚 what happens:
  • Potassium donates electrons to water molecules.
  • The hydrogen atoms in water are reduced, forming hydrogen gas \( \text{H}_2 \).
  • Oxygen combines with potassium to form potassium hydroxide (KOH).
Potassium hydroxide is a strong base, indicating its ability to increase the pH of a solution, making it more basic. Understanding hydroxide formation is important in chemistry as it helps explain many properties and reactions of alkali metals.

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Most popular questions from this chapter

Use the building-up principle to obtain the electron configuration of the ground state of manganese.

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