Question

When heated, platinum(IV) chloride undergoes a decomposition reaction. Write a balanced equation to describe this reaction.

Short answer

The balanced equation for the decomposition of platinum(IV) chloride is: PtCl4 -> Pt + 2Cl2.

Step-by-step solution

Identify the Decomposition Reaction

Platinum(IV) chloride decomposes when heated. In a decomposition reaction, a single compound breaks down into two or more simpler substances. Platinum(IV) indicates that platinum has an oxidation state of +4. In platinum(IV) chloride, the roman numeral (IV) indicates that the platinum ion has a charge of +4. Chlorine ions always have a charge of -1. Therefore, the compound PtCl4 (platinum(IV) chloride) is formed.

Write the Initial Unbalanced Decomposition Equation

In the case of decomposition of platinum(IV) chloride, it decomposes into platinum and chlorine gas when heated. The unbalanced chemical reaction will look like this: PtCl4 -> Pt + Cl2

Balance the Equation

Now we balance the number of each type of atom on both sides of the equation. On the left side, there are 1 Pt and 4 Cl atoms. On the right, there is 1 Pt and 2 Cl atoms. To correct this, we add a coefficient of 2 to Cl2 on the right side of the equation. The balanced equation therefore becomes: PtCl4 -> Pt + 2Cl2

Key concepts

Chemical Equations

Understanding chemical equations is essential for studying chemical reactions. A chemical equation provides a symbolic representation of a chemical reaction, showcasing the reactants transforming into the products. It's a balance between atoms and molecules on both sides – what you start with and what you end up with should be equal.

Take the decomposition of platinum(IV) chloride, for instance. The reactant here is PtCl4, and the products are Pt and Cl2. The equation initially looks unbalanced:
PtCl4 -> Pt + Cl2. To comply with the law of conservation of mass, we must ensure that the number of atoms for each element is the same on both sides. This is achieved through balancing the equation, which often requires adding coefficients in front of the chemical formulas to ensure that the same number and types of atoms appear on both sides of the arrow, thus conserving mass.

Oxidation State

The concept of oxidation state, also known as oxidation number, is vital in understanding chemical reactions, especially redox reactions. It signifies the degree of oxidation of an atom within a substance. It's a bookkeeping device to track how electrons are transferred in chemical reactions, with positive or negative values that can help us infer the type of bonding and the distribution of electrons among atoms in a molecule.

For instance, in the compound platinum(IV) chloride, PtCl4, the (IV) denotes platinum's oxidation state, indicating it is losing four electrons and is therefore positively charged. Chlorine, typically having a -1 oxidation state, means each chlorine atom is accepting one electron. These oxidation states ensure that the overall charge of the compound is neutral and provide insight into the electron transfer taking place during the decomposition reaction.

Balancing Chemical Reactions

Balancing chemical reactions is a fundamental skill in chemistry. It ensures that the Law of Conservation of Mass is followed, meaning the mass of substances produced in a chemical reaction equals the mass of reacting substances. Let's apply this to the provided exercise where we balance the decomposition of platinum(IV) chloride:
PtCl4 -> Pt + 2Cl2.

Initially, the reaction is not balanced because there are four chlorine atoms in the reactant but only two in the product. By adding a coefficient of 2 in front of Cl2, we now have an equal number of chlorine atoms on both sides, satisfying the balancing requirement. It's critical for students to practice this skill to accurately predict the quantities of reactants needed and the amount of products formed in a given chemical reaction.