Problem 5 - Chemistry and Chemical Reactivity

Question

Give examples of two basic oxides. Write equations illustrating the formation of each oxide from its component elements. Write another chemical equation that illustrates the basic character of each oxide.

Step-by-Step Solution

Answer

Examples: CaO and MgO. Formation: Ca + 1/2 O₂ → CaO; Mg + 1/2 O₂ → MgO. Basic character: CaO + 2HCl → CaCl₂ + H₂O; MgO + 2HCl → MgCl₂ + H₂O.

Step 1: Identify Basic Oxides

Basic oxides are oxides that react with acids to form salt and water. Examples of basic oxides include calcium oxide (CaO) and magnesium oxide (MgO).

Step 2: Write Equations for Formation from Elements

Write the chemical equations that show the formation of each oxide from its elements. For calcium oxide: \ \[ \text{Ca (s)} + \frac{1}{2} \text{O}_2 \text{(g)} \rightarrow \text{CaO (s)} \] \ For magnesium oxide: \ \[ \text{Mg (s)} + \frac{1}{2} \text{O}_2 \text{(g)} \rightarrow \text{MgO (s)} \]

Step 3: Illustrate Basic Character

Write a chemical equation that illustrates the basic character of each oxide, showing how they react with acids. Calcium oxide reacting with hydrochloric acid: \ \[ \text{CaO (s)} + 2\text{HCl (aq)} \rightarrow \text{CaCl}_2 \text{(aq)} + \text{H}_2\text{O (l)} \] \ Magnesium oxide reacting with hydrochloric acid: \ \[ \text{MgO (s)} + 2\text{HCl (aq)} \rightarrow \text{MgCl}_2 \text{(aq)} + \text{H}_2 ext{O (l)} \]

Key Concepts

Chemical Equations

Chemical equations are symbolic representations of chemical reactions. A chemical equation shows the substances that react (called reactants) and those that are formed (called products). It's crucial to balance these equations to obey the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. Each element must have the same number of atoms on both sides of the equation.
For example, the formation of calcium oxide involves calcium and oxygen producing calcium oxide. The reaction is expressed as:

• Reactants: Ca (calcium) and \( \frac{1}{2} \text{O}_2 \) (oxygen)
• Product: CaO (calcium oxide)

The balanced equation for this reaction is:\[\text{Ca (s)} + \frac{1}{2} \text{O}_2 \text{(g)} \rightarrow \text{CaO (s)}\]Similarly, magnesium and oxygen react to form magnesium oxide:

• Reactants: Mg (magnesium) and \( \frac{1}{2} \text{O}_2 \) (oxygen)
• Product: MgO (magnesium oxide)

The balanced equation is:\[\text{Mg (s)} + \frac{1}{2} \text{O}_2 \text{(g)} \rightarrow \text{MgO (s)}\]
Balancing these equations ensures that the laws of chemistry are upheld, making the reactions predictable and understandable.

Oxide Formation

Oxide formation refers to the chemical process where elements react with oxygen to form oxides. Oxides can be classified based on their chemical nature into basic, acidic, or neutral oxides. Basic oxides, such as calcium oxide (CaO) and magnesium oxide (MgO), are typically formed by metals reacting with oxygen. Let's explore the formation of these two basic oxides.
Formation of Calcium Oxide (CaO): When calcium, a reactive metal, burns in the presence of oxygen, it forms calcium oxide, a white crystalline solid. This reaction can be represented by the equation:\[\text{Ca (s)} + \frac{1}{2} \text{O}_2 \text{(g)} \rightarrow \text{CaO (s)}\]

• Calcium reacts directly with oxygen from the air.
• The process typically requires heat to initiate the reaction.

Formation of Magnesium Oxide (MgO): Similarly, when magnesium burns in the air, it reacts with oxygen to form magnesium oxide, a white powder. The equation for this reaction is:\[\text{Mg (s)} + \frac{1}{2} \text{O}_2 \text{(g)} \rightarrow \text{MgO (s)}\]

• Magnesium must be ignited to start the reaction with oxygen.
• This reaction emits bright light, characteristic of burning magnesium.

Oxide formation is an exothermic process, meaning it releases heat, making these reactions highly energetic.

Acid-Base Reactions

Acid-base reactions are chemical reactions that occur between an acid and a base. In these reactions, an acid reacts with a base to form a salt and water, neutralizing the acidic and basic properties. Basic oxides typically react with acids in such reactions, thereby demonstrating their fundamental chemical nature.
Calcium Oxide (CaO) Reaction with Hydrochloric Acid (HCl): When calcium oxide, a basic oxide, reacts with hydrochloric acid, a salt and water are produced:\[\text{CaO (s)} + 2\text{HCl (aq)} \rightarrow \text{CaCl}_2 \text{(aq)} + \text{H}_2\text{O (l)}\]

• This reaction forms calcium chloride, a salt, and water.
• The basic nature of CaO counteracts the acidity of HCl.

Magnesium Oxide (MgO) Reaction with Hydrochloric Acid (HCl):Similarly, magnesium oxide reacts with hydrochloric acid in the following reaction:\[\text{MgO (s)} + 2\text{HCl (aq)} \rightarrow \text{MgCl}_2 \text{(aq)} + \text{H}_2 \text{O (l)}\]

• Forms magnesium chloride, a salt, and water.
• Again, the reaction highlights the neutralizing effect of MgO on the acid.

These reactions exemplify how basic oxides interact with acids, affirming their classification as basic.