Question

Balance the equation for the reaction of potassium with water. $$\mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+\mathrm{KOH}(a q)$$

Short answer

The balanced equation for the reaction of potassium with water is: \( \mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+2\mathrm{KOH}(a q) \)

Step-by-step solution

Write down the unbalanced equation

First, write down the given unbalanced equation: \( \mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+\mathrm{KOH}(a q) \) Now, we will balance the equation by adjusting the coefficients in front of each chemical species.

Balance potassium atoms

There is 1 potassium atom on the reactant side and 1 potassium atom on the product side in the KOH molecule. So, potassium atoms are already balanced: \( \mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+\mathrm{KOH}(a q) \)

Balance hydrogen atoms

On the reactant side, there are 2 hydrogen atoms present in the water molecule. On the product side, there are 2 hydrogen atoms present in the hydrogen gas molecule and another 1 hydrogen atom in the KOH molecule, making a total of 3 hydrogen atoms. To balance the hydrogen atoms, place a coefficient of 2 in front of KOH on the product side of the equation: \( \mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+2\mathrm{KOH}(a q) \) Now, there are 2 hydrogen atoms on the reactant side and 4 hydrogen atoms on the product side.

Balance oxygen atoms

There is 1 oxygen atom on the reactant side, present in the water molecule. On the product side, there are 2 oxygen atoms, one in each KOH molecule. The oxygen atoms are already balanced: \( \mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+2\mathrm{KOH}(a q) \)

Final check

Double-check to ensure all elemental atoms have been balanced. On both sides of the equation, there is: - 1 potassium atom - 2 hydrogen atoms in water and hydrogen gas, and 2 in the 2 KOH molecules (total of 4 hydrogen atoms) - 1 oxygen atom The balanced equation is: \( \mathrm{K}(s)+\mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2}(g)+2\mathrm{KOH}(a q) \)

Key concepts

Stoichiometry

Stoichiometry is a fundamental concept in chemistry that deals with the quantitative relationships between the substances involved in chemical reactions. It helps us understand how much of each substance is needed or produced in a reaction based on balanced chemical equations. This is essential for accurately predicting the amounts of reactants required and products formed. When balancing chemical equations, stoichiometry plays a crucial role. We adjust the coefficients of each compound to ensure that the number of atoms for each element is equal on both sides of the equation. This is important for maintaining the law of conservation of mass. By understanding stoichiometry, we can make precise calculations about reactions in real-world applications, from laboratory experiments to industrial processes.

Chemical Reactions

Chemical reactions are processes in which substances, known as reactants, transform into different substances, known as products. These reactions involve the breaking and forming of chemical bonds, which rearranges the atoms into new configurations. In the reaction between potassium and water given in the exercise, potassium metal reacts with water to produce hydrogen gas and potassium hydroxide. This is a type of single replacement reaction where potassium replaces hydrogen in water. Chemical reactions can be classified into different types based on the nature of the changes and the products formed, including synthesis, decomposition, single replacement, and double replacement. Learning to write and balance chemical equations helps chemists describe chemical reactions accurately. It provides a clear understanding of how different substances interact and what transformations occur during the reaction.

Conservation of Mass

The principle of conservation of mass states that mass in a closed system must remain constant over time. This means that matter cannot be created or destroyed, only rearranged. In chemical reactions, this principle indicates that the mass of the reactants must equal the mass of the products. When balancing chemical equations like the one involving potassium and water, ensuring that the number of each type of atom is the same on both sides of the equation respects this fundamental law. If we start with a certain number of potassium atoms, hydrogen atoms, and oxygen atoms as reactants, we must have the same number of each type of atom in the products. This concept is crucial not only to balance equations but also to understand that during any chemical reaction, the total mass of the involved substances does not change. Properly balanced equations ensure that the conservation of mass is accurately represented.