Question

Write a balanced equation for each of the following single-replacement reactions: (a) Zinc granules are placed in carbonic acid. (b) Cadmium metal is added to acetic acid.

Short answer

(a) \( \text{Zn} + \text{H}_2\text{CO}_3 \rightarrow \text{ZnCO}_3 + \text{H}_2 \) (b) \( \text{Cd} + 2\text{HC}_2\text{H}_3\text{O}_2 \rightarrow \text{Cd(C}_2\text{H}_3\text{O}_2)_2 + \text{H}_2 \)

Step-by-step solution

Write the Unbalanced Equation for Part (a)

First, identify the initial reactants and products. Zinc (Zn) reacts with carbonic acid (H_2CO_3). Zinc will replace hydrogen, producing zinc carbonate (ZnCO_3) and hydrogen gas (H_2). Therefore, the unbalanced equation for this reaction is: \[ \text{Zn} + \text{H}_2\text{CO}_3 \rightarrow \text{ZnCO}_3 + \text{H}_2 \]

Balance the Equation for Part (a)

To balance the equation, ensure the number of each type of atom is the same on each side. There is one zinc (Zn), one carbonate (CO_3), and two hydrogen (H) atoms on each side. Thus, the balanced equation is: \[ \text{Zn} + \text{H}_2\text{CO}_3 \rightarrow \text{ZnCO}_3 + \text{H}_2 \]

Write the Unbalanced Equation for Part (b)

Second, identify the reactants and products for the reaction between cadmium (Cd) and acetic acid (HC_2H_3O_2). Cadmium will replace hydrogen in the acid, yielding cadmium acetate (Cd(C_2H_3O_2)_2) and hydrogen gas (H_2). The unbalanced equation is: \[ \text{Cd} + \text{HC}_2\text{H}_3\text{O}_2 \rightarrow \text{Cd(C}_2\text{H}_3\text{O}_2)_2 + \text{H}_2 \]

Balance the Equation for Part (b)

Balance the elements in the reaction by ensuring each type of atom is equal on both sides. On the reactant side, you need two acetic acid molecules to provide the acetate for the product and to balance the hydrogen gas (H_2). The balanced equation is: \[ \text{Cd} + 2\text{HC}_2\text{H}_3\text{O}_2 \rightarrow \text{Cd(C}_2\text{H}_3\text{O}_2)_2 + \text{H}_2 \]

Key concepts

Single Replacement

A single replacement reaction, also known as a single displacement reaction, is a type of chemical reaction where an element reacts with a compound and takes the place of another element in that compound. This type of reaction typically involves metals and acids or salts. One of the key features of single replacement reactions is that they follow a pattern: a more reactive element replaces a less reactive element in a compound. This reactivity is often predicted using the reactivity series for metals and is determined by the ability of an element to lose or gain electrons.

• In the case of zinc reacting with carbonic acid, zinc replaces the hydrogen in the acid, forming zinc carbonate and hydrogen gas.
• Similarly, when cadmium reacts with acetic acid, cadmium takes the place of hydrogen, resulting in cadmium acetate and hydrogen gas.

Understanding the reactivity series helps predict whether a particular single replacement reaction will occur, as not all elements can displace others. Elements higher in the series will typically replace those lower down in a compound.

Balancing Chemical Equations

Balancing chemical equations is an essential skill in chemistry that ensures the law of conservation of mass is maintained. According to this law, matter cannot be created or destroyed in a chemical reaction. Therefore, a balanced chemical equation will have the same number of each type of atom on both sides of the equation.

• To balance an equation, you start by writing the unbalanced equation with all reactants and products. Then, adjust coefficients—the numbers in front of molecules—to equalize the number of atoms of each element on both sides.
• For instance, in the reaction between zinc and carbonic acid, both sides naturally have an equal number of each atom, making the equation balanced from the start without need for additional coefficients.
• In the case of cadmium and acetic acid, you need to use two molecules of acetic acid to provide the appropriate acetate ions and balance the hydrogen gas molecule produced.

Balancing chemical equations requires practice, but once mastered, it becomes easier to quickly and accurately represent chemical reactions.

Inorganic Chemistry

Inorganic chemistry focuses on the behavior and synthesis of inorganic and organometallic compounds. These include minerals, metals, and other compounds that do not fit into the category of organic compounds.

• Many reactions in inorganic chemistry, like single replacement reactions, involve metals and acids. Understanding the properties and reactivity of various inorganic substances is crucial to predict product formation.
• The reactions of zinc with carbonic acid and cadmium with acetic acid are typical examples of inorganic reactions involving metals displacing hydrogen ions from acids.

Despite the randomness of organic compounds, inorganic chemistry often deals with crystal structures and symmetry. This field is vast and includes many sub-disciplines such as coordination chemistry, organometallic, and bioinorganic chemistry. Mastery of the fundamentals in inorganic chemistry provides a solid foundation for exploring the more complex interactions in this branch of science.