Problem 10 - Chemistry and Chemical Reactivity

Question

Select one of the alkaline earth metals and write a balanced chemical equation for its reaction with oxygen. Is the reaction likely to be exothermic or endothermic? Is the product ionic or molecular?

Step-by-Step Solution

Answer

Mg reacts with O₂ to form MgO, which is ionic and exothermic.

Step 1: Select an Alkaline Earth Metal

We will select magnesium (Mg) as our alkaline earth metal for this exercise. Magnesium is a common example of this group and often used to demonstrate reactions with oxygen.

Step 2: Write the Chemical Equation

The chemical equation for the reaction between magnesium and oxygen is written as follows:\[ 2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO} \]This equation shows that two moles of magnesium react with one mole of oxygen gas to produce two moles of magnesium oxide.

Step 3: Balance the Chemical Equation

The chemical equation is already balanced as written in Step 2. There are two magnesium atoms and two oxygen atoms on both the reactant and product sides of the equation, indicating that the equation follows the law of conservation of mass.

Step 4: Determine the Nature of the Reaction (Exothermic or Endothermic)

The reaction between magnesium and oxygen is highly exothermic. It releases a significant amount of energy in the form of heat and light, which is why burning magnesium produces a bright white flame.

Step 5: Identify the Type of Product (Ionic or Molecular)

The product, magnesium oxide (MgO), is ionic. This is because it is formed by the transfer of electrons: magnesium loses two electrons to form Mg²⁺ ions, and oxygen gains those electrons to form O²⁻ ions, resulting in the ionic compound MgO.

Key Concepts

Magnesium

Magnesium is a key alkaline earth metal found in group 2 of the periodic table. It’s often used in chemistry due to its reactivity, especially with oxygen.
When studying magnesium, remember these points:

• Symbol: Mg
• Atomic number: 12
• Silvery-white appearance
• Commonly found in minerals like dolomite and magnesite

Magnesium is not only essential in chemical reactions but also in biological processes. It plays a vital role in helping our body function, particularly in muscle and nerve operations.

Chemical Reactions

Chemical reactions involve the transformation of substances through the breaking and forming of bonds. In the case of magnesium reacting with oxygen, the following process occurs:- Magnesium (Mg) reacts with oxygen (O_2)- The reaction produces magnesium oxide (MgO)The balanced equation is:\[2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}\]Balancing chemical equations ensures the law of conservation of mass is obeyed, meaning the same number of each type of atom is present before and after the reaction.

Exothermic Reactions

An exothermic reaction is one that releases energy, usually as heat or light. The reaction between magnesium and oxygen is a prime example.
Here's what to note about exothermic reactions:

• Release energy to the surroundings
• Products have less energy than reactants
• Temperature increase is often noticeable
• Commonly seen with combustion reactions, like burning magnesium

The bright white flame seen when magnesium burns is due to this energy release, capturing students' attention with its dramatic effect.

Ionic Compounds

Ionic compounds form through the transfer of electrons, resulting in positively and negatively charged ions. Magnesium oxide (MgO) is one such ionic compound.
Here's how it works:

• Magnesium loses two electrons to become Mg²⁺
• Oxygen gains two electrons to become O²⁻
• These oppositely charged ions attract, forming a strong ionic bond

Ionic compounds like MgO are generally solid at room temperature and have high melting points due to the strong electrostatic forces between ions.