Question

Complete and balance the equation for each of the following combination reactions. (a) \(\mathrm{Na}(s)+\mathrm{O}_{2}(g) \longrightarrow\) (b) \(\mathrm{Al}(s)+\mathrm{Cl}_{2}(g) \longrightarrow\) (c) \(\mathrm{Ca}(s)+\mathrm{F}_{2}(\mathrm{~g}) \longrightarrow\)

Short answer

The balanced chemical equations are (a) 4Na + O2 \(\longrightarrow\) 2Na2O (b) 2Al + 3Cl2 \(\longrightarrow\) 2AlCl3 (c) Ca + F2 \(\longrightarrow\) CaF2.

Step-by-step solution

Complete the reactions

Firstly, complete the reactions by writing correct products. Sodium (Na) reacts with oxygen (O2) to form sodium oxide (Na2O). Aluminium (Al) reacts with chlorine (Cl2) to form aluminium chloride (AlCl3). Calcium (Ca) reacts with Fluorine (F2) to form calcium fluoride (CaF2).

Balance the equations

Now, balance the equations by adjusting the coefficients. In reaction (a), put 4 in front of Na (reactant side) and 2 in front of Na2O (product side). In reaction (b), put 2 in front of Al (reactant side) and 3 in front of Cl2 (reactant side). In reaction (c), make sure that there are 2 F atoms on both sides. These become: (a) 4Na + O2 \(\longrightarrow\) 2Na2O (b) 2Al + 3Cl2 \(\longrightarrow\) 2AlCl3 (c) Ca + F2 \(\longrightarrow\) CaF2

Check the balance

Finally, double check each equation to make sure the number of each type of atom is the same on both sides. For example, in reaction (a), there are 4 sodium atoms and 2 oxygen atoms on both sides, so it's balanced.

Key concepts

Combination Reactions

Combination reactions, also known as synthesis reactions, occur when two or more reactants combine to form a single product. This type of chemical reaction usually involves either elements or simple compounds coming together. For instance, in the provided exercise, sodium (Na) reacts with oxygen (\( \text{O}_2 \)) to produce sodium oxide (\( \text{Na}_2\text{O} \)). Similarly, aluminum (Al) and chlorine (\( \text{Cl}_2 \)) unite to form aluminum chloride (\( \text{AlCl}_3 \)). Finally, calcium (Ca) combines with fluorine (\( \text{F}_2 \)) to yield calcium fluoride (\( \text{CaF}_2 \)).

• Combination reactions are straightforward: two reactants result in one product.
• They often involve metals reacting with nonmetals to form ionic compounds.

Understanding combination reactions helps in predicting products in chemical processes. It's a fundamental aspect of understanding how substances interact at the molecular level.

Balancing Chemical Equations

Balancing chemical equations is essential to the principle of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. A balanced equation has the same number of atoms for each element on both sides of the equation. This ensures that the equation accurately represents the chemical reaction.
In the exercise, balancing starts after completing the reactions. For instance:

• In reaction (a), 4 moles of Na react with 1 mole of \( \text{O}_2 \) to form 2 moles of \( \text{Na}_2\text{O} \). Thus,\( 4\text{Na} + \text{O}_2 \rightarrow 2\text{Na}_2\text{O} \).
• In reaction (b), 2 moles of Al react with 3 moles of \( \text{Cl}_2 \) to form 2 moles of \( \text{AlCl}_3 \). Therefore,\( 2\text{Al} + 3\text{Cl}_2 \rightarrow 2\text{AlCl}_3 \).
• In reaction (c), the equation is naturally balanced as \( \text{Ca} + \text{F}_2 \rightarrow \text{CaF}_2 \).

To balance, adjust the coefficients (the numbers in front of substances) without changing any formulas. Mastery of this skill is crucial for accurately describing chemical phenomena.

Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It helps in determining the proportions in which chemicals combine and react, based on the balanced chemical equation.
When the equation is balanced, stoichiometry allows us to calculate the exact amount of reactants needed to produce a desired amount of product, or vice versa. This aspect is illustrated in the exercise by:

• Using the coefficients from the balanced equations as conversion factors. For example, in reaction (a), the ratio is 4:1:2 for \( \text{Na} \), \( \text{O}_2 \), and \( \text{Na}_2\text{O} \) respectively.
• For reaction (b), the stoichiometric ratio is 2:3:2, which indicates that two moles of Al react with three moles of \( \text{Cl}_2 \) to yield two moles of \( \text{AlCl}_3 \).
• Even in simpler reactions like (c), stoichiometry confirms that one mole of \( \text{Ca} \) reacts with one mole of \( \text{F}_2 \) to form one mole of \( \text{CaF}_2 \).

Stoichiometry connects chemical equations to real-world applications by allowing scientists to scale reactions up or down, ensuring precise calculations for experimental and industrial purposes.