Question

Complete and balance each of the following singledisplacement reactions. (a) \(\mathrm{Al}(s)+\mathrm{CuSO}_{4}(a q) \longrightarrow\) (b) \(\mathrm{Cs}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow\)

Short answer

The completed and balanced single displacement reactions are: (a) \(\mathrm{Al}(s)+\mathrm{CuSO}_{4}(a q) \longrightarrow \mathrm{AlSO}_{4}(a q)+\mathrm{Cu}(s)\) (b) \(\mathrm{Cs}(s)+2\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2\mathrm{CsOH}(a q)+\mathrm{H}_{2}(g)\)

Step-by-step solution

Identify Possible Products

A single displacement reaction involves one element replacing another element in a compound. Observation of the reactivity series shows that Aluminum (Al) is more reactive than Copper (Cu), hence Al can displace Cu in CuSO4. For the reaction, \(\mathrm{Al}(s)+\mathrm{CuSO}_{4}(a q)\), the products are \(\mathrm{AlSO}_{4}(a q)\) and \(\mathrm{Cu}(s)\). Similarly, Cesium (Cs) is a highly reactive alkali metal that reacts vigorously with water to produce Cesium Hydroxide (CsOH) and Hydrogen gas (H2). Therefore, the products of the reaction \(\mathrm{Cs}(s)+\mathrm{H}_{2} \mathrm{O}(l)\) are \(\mathrm{CsOH}(a q)\) and \(\mathrm{H}_{2}(g)\).

Complete the Chemical Equation

Insert the identified products to their respective reactions. The completed chemical equations are: (a) \(\mathrm{Al}(s)+\mathrm{CuSO}_{4}(a q) \longrightarrow \mathrm{AlSO}_{4}(a q)+\mathrm{Cu}(s)\) (b) \(\mathrm{Cs}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{CsOH}(a q)+\mathrm{H}_{2}(g)\)

Balance the Chemical Equations

To balance the equations, ensure that the number of atoms of each element is the same on both sides of the equation. For equation (a), It's already balanced. For equation (b), balancing the hydrogen atoms leads to: \(\mathrm{Cs}(s)+2\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2\mathrm{CsOH}(a q)+\mathrm{H}_{2}(g)\)

Key concepts

Chemical Equation Balancing

In chemistry, balancing chemical equations is a fundamental skill that is crucial for understanding how reactions proceed. It involves ensuring that the number of atoms for each element is conserved, adhering to the Law of Conservation of Mass. To balance an equation, you can only adjust the coefficients (the numbers in front of chemicals), not the subscripts (which are part of the chemical formulas).

For single displacement reactions, such as the textbook examples of aluminum reacting with copper sulfate and cesium reacting with water, we must ensure that both atoms and charges balance. In these reactions, it's not just the count of each type of atom that matters, but also the overall charge. In simple cases, the reactions might be inherently balanced, as with aluminum and copper sulfate. However, in other instances, like the cesium and water reaction, we must add coefficients to balance the hydrogen atoms.

Steps to Balance Equations:

• Write down the number of atoms of each element on both sides of the equation.
• Start by balancing elements that appear only in one reactant and product.
• Balance multi-atom molecules last (like H₂O).
• Use coefficients to balance the atoms, never change subscripts.
• Double-check to ensure that both the atoms and charges are balanced.

By following these steps, one can systematically approach balancing any chemical equation.

Reactivity Series

The reactivity series is a valuable tool for predicting the products of single displacement reactions. It ranks elements, particularly metals, by their tendency to displace others in a chemical reaction. Knowing where elements fall in this series enables us to predict whether a certain reaction will occur and which element will be displaced.

For example, aluminum (Al) has a higher reactivity than copper (Cu), so it can displace copper from copper sulfate (CuSO₄). When examining a potential single displacement reaction, refer to the reactivity series: if the free element is more reactive than the bound element, the reaction can proceed.

Important Points about the Reactivity Series:

• Highly reactive elements, like alkali metals and alkaline earth metals, are typically at the top.
• Noble metals, like gold and platinum, are found at the bottom as they rarely participate in such reactions.
• The reactivity series helps in understanding corrosion and metal extraction processes as well.

Knowledge of the reactivity series is not just crucial for predicting reactions; it's also essential for safety, as some displacements can be vigorous or even dangerous.

Alkali Metals

Alkali metals make up Group 1 of the periodic table and include elements like lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). They are known for being extremely reactive, especially with water, and this reactivity increases as you move down the group.

The reaction of cesium (Cs) with water is a telltale example of the reactivity of alkali metals. These metals react with water to form hydroxides and hydrogen gas. Cesium's position in the periodic table makes it one of the most reactive elements. This behavior can be explained in terms of atomic structure; alkali metals have a single electron in their outermost shell that they readily lose, making them highly reactive.

Characteristics of Alkali Metals:

• They are shiny and soft enough to be cut with a knife.
• These metals have low melting points relative to most other metals.
• They readily lose their outermost electron to form cations with a charge of +1, which lends to their high reactivity.
• Alkali metals must be stored under oil or in an inert atmosphere to prevent them from reacting with air or moisture.

When handling alkali metals or predicting their reactions, one must always consider their place in the reactivity series and the safety precautions due to their vigorous behavior.