Problem 11 - Chemistry and Chemical Reactivity

Question

Balance the following equations, and name each reactant and product: (a) \(\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{s})+\mathrm{Mg}(\mathrm{s}) \rightarrow \mathrm{MgO}(\mathrm{s})+\mathrm{Fe}(\mathrm{s})\) (b) \(\mathrm{AlCl}_{3}(\mathrm{s})+\mathrm{NaOH}(\mathrm{aq}) \rightarrow\) \(\mathrm{Al}(\mathrm{OH})_{3}(\mathrm{s})+\mathrm{NaCl}(\mathrm{aq})\) (c) \(\mathrm{NaNO}_{3}(\mathrm{s})+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \rightarrow\) \(\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{s})+\mathrm{HNO}_{3}(\mathrm{aq})\) (d) \(\mathrm{NiCO}_{3}(\mathrm{s})+\mathrm{HNO}_{3}(\mathrm{aq}) \rightarrow\) \(\mathrm{Ni}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)\)

Step-by-Step Solution

Answer

Balanced equations are: (a) \( \mathrm{Fe}_2\mathrm{O}_3+3\mathrm{Mg}\rightarrow3\mathrm{MgO}+2\mathrm{Fe}\), (b) \( \mathrm{AlCl}_3+3 \mathrm{NaOH}\rightarrow \mathrm{Al(OH)_3}+3\mathrm{NaCl}\), (c) \( 2\mathrm{NaNO}_3+\mathrm{H}_2\mathrm{SO}_4\rightarrow\mathrm{Na}_2\mathrm{SO}_4+2\mathrm{HNO}_3\), (d) \( \mathrm{NiCO}_3+2\mathrm{HNO}_3\rightarrow\mathrm{Ni(NO}_3)_2+\mathrm{CO}_2+\mathrm{H}_2\mathrm{O}\).

Step 1: Balance Equation (a)

First, identify the reactants and products. The reactants are iron(III) oxide (\( \mathrm{Fe}_2 \mathrm{O}_3 \)) and magnesium (\( \mathrm{Mg} \)), while the products are magnesium oxide (\( \mathrm{MgO} \)) and iron (\( \mathrm{Fe} \)). To balance the equation: 1. Balance Mg: You need 3 magnesium atoms, therefore, 3 \( \mathrm{Mg} \) on the reactant side.\[ \mathrm{Fe}_2 \mathrm{O}_3 + 3 \mathrm{Mg} \rightarrow 3 \mathrm{MgO} + 2 \mathrm{Fe} \]Now the equation is balanced.

Step 2: Balance Equation (b)

Identify the reactants Aluminum chloride (\( \mathrm{AlCl}_3 \)) and sodium hydroxide (\( \mathrm{NaOH} \)), and the products aluminum hydroxide (\( \mathrm{Al(OH)_3} \)) and sodium chloride (\( \mathrm{NaCl} \)). Balance as follows:1. Balance Al: One \( \mathrm{Al} \) on both sides.2. Balance Cl: 3 sodium chlorides are needed, hence 3 \( \mathrm{NaOH} \) and 3 \( \mathrm{NaCl}\).\[ \mathrm{AlCl}_3 + 3 \mathrm{NaOH} \rightarrow \mathrm{Al(OH)_3} + 3 \mathrm{NaCl} \]The equation is balanced.

Step 3: Balance Equation (c)

Reactants are sodium nitrate (\( \mathrm{NaNO}_3 \)) and sulfuric acid (\( \mathrm{H}_2 \mathrm{SO}_4 \)), products are sodium sulfate (\( \mathrm{Na}_2 \mathrm{SO}_4 \)) and nitric acid (\( \mathrm{HNO}_3 \)).1. Balance Na and \( \mathrm{H} \): Two \( \mathrm{Na} \) needed thus 2 \( \mathrm{NaNO}_3 \). Then balance \( \mathrm{H} \) accordingly.\[ 2 \mathrm{NaNO}_3 + \mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{Na}_2 \mathrm{SO}_4 + 2 \mathrm{HNO}_3 \]The equation is balanced.

Step 4: Balance Equation (d)

Identify Nickel carbonate (\( \mathrm{NiCO}_3 \)) and nitric acid (\( \mathrm{HNO}_3 \)) as reactants, products nickel(II) nitrate (\( \mathrm{Ni(NO}_3)_{2} \)), carbon dioxide (\( \mathrm{CO}_2 \)), and water (\( \mathrm{H}_2 \mathrm{O} \)).1. Balance Ni and C first: same on both.2. Balance \( \mathrm{H} \) and \( \mathrm{N} \): Two \( \mathrm{HNO}_3 \) is needed from product side.\[ \mathrm{NiCO}_3 + 2 \mathrm{HNO}_3 \rightarrow \mathrm{Ni(NO}_3)_2 + \mathrm{CO}_2 + \mathrm{H}_2 \mathrm{O} \]The equation is balanced.

Key Concepts

Reactants and Products

In any chemical reaction, the substances you start with are called the reactants. Reactants are the ingredients placed into the chemical equation. During the reaction, these reactants undergo a transformation to form new substances called products. Products are the end result of the process.

For example, in the reaction of iron(III) oxide and magnesium, our reactants are iron(III) oxide (\( \mathrm{Fe}_2 \mathrm{O}_3 \)) and magnesium (\( \mathrm{Mg} \)), and the end products are magnesium oxide (\( \mathrm{MgO} \)) and iron (\( \mathrm{Fe} \)).

Being able to identify reactants and products is crucial for balancing chemical equations as it helps us see how atoms are rearranged during the reaction.

Stoichiometry

Stoichiometry is a core concept that involves the quantitative relationship between reactants and products in a chemical reaction. It allows us to predict the amounts of products produced based on the amounts of reactants used.

To balance a chemical equation, it's important to ensure that the number of atoms of each element is the same on both sides of the equation. This requires adjusting coefficients, which are the numbers placed in front of the chemical formulas in the equation. For example, in the balanced equation \( \mathrm{Fe}_2 \mathrm{O}_3 + 3 \mathrm{Mg} \rightarrow 3 \mathrm{MgO} + 2 \mathrm{Fe} \),
the stoichiometric coefficients (3 and 2) indicate the ratio in which magnesium and iron are produced.

Mastering stoichiometry gives us insight into how much of each substance is needed or produced, thus allowing for an efficient approach to chemical reactions.

Chemical Reactions

Chemical reactions occur when substances interact to form new products. These reactions involve the breaking and forming of chemical bonds. The process can be represented by chemical equations which provide a concise way of describing the transformation from reactants to products.

To understand these transformations, it is essential to observe certain characteristics of chemical reactions:

• Change in color or appearance of substances
• Release or absorption of energy (heat, light, etc.)
• Formation of precipitates or gases

In the case of aluminum chloride reacting with sodium hydroxide, the formation of aluminum hydroxide and sodium chloride is the new arrangement of bonds and entities, underscoring the chemical reaction.

Chemical Compounds

Chemical compounds consist of two or more elements chemically bonded together. These compounds have their own unique properties different from the individual elements that constitute them. Understanding these properties is vital to predicting how compounds will behave in reactions.

For instance, water (\( \mathrm{H}_2 \mathrm{O} \)), a compound formed from hydrogen and oxygen, exhibits properties radically different from either gaseous hydrogen or oxygen. Similarly, sodium chloride (\( \mathrm{NaCl} \)), common table salt, arises from the binding of sodium and chlorine in a compound with new properties, such as being crystalline and soluble in water.

Recognizing the structures and properties of chemical compounds enables chemists to determine the feasibility and potential outcomes of reactions involving them.