Question

a. What is meant by the term coefficient in relation to a chemical equation? b. How does the presence of a coefficient affect the number of atoms of each type in the formula that the coefficient precedes?

Short answer

In a chemical equation, a coefficient is a number before a formula indicating the quantity of molecules or atoms. It multiplies each atom count in the formula.

Step-by-step solution

Understanding the Term 'Coefficient' in a Chemical Equation

In chemistry, a coefficient is a number placed in front of a chemical formula in a chemical equation. It indicates how many molecules or atoms of the substance are involved in the reaction. For example, in the equation \(2H_2 + O_2 \rightarrow 2H_2O\), the coefficient '2' before \(H_2\) and \(H_2O\) indicates that there are 2 molecules of hydrogen and 2 molecules of water.

Effect of Coefficients on the Number of Atoms

The coefficient affects the number of each type of atom in the formula it precedes by multiplying each atom in the formula by the coefficient. For instance, if the coefficient of \( \text{H}_2O \) is 2, then the total number of hydrogen atoms is \(2 \times 2 = 4\) and the total number of oxygen atoms is \(2 \times 1 = 2\). The coefficients ensure that the law of conservation of mass is satisfied, meaning the number of each type of atom remains constant before and after the reaction.

Key concepts

chemical equation

A chemical equation is a symbolic representation of a chemical reaction. It shows the reactants (substances that start a reaction) on the left side and the products (substances formed by the reaction) on the right side. The reactants and products are connected by an arrow, which indicates the direction of the reaction.
For example, in the equation \(2H_2 + O_2 \rightarrow 2H_2O\), \(H_2\) and \(O_2\) are the reactants, and \(H_2O\) is the product.

• The coefficients in front of the formulas indicate the number of molecules or moles of each substance involved.
• The subscripts within the formulas show the number of each type of atom in a molecule.

The main purpose of a chemical equation is to provide a clear and concise way to describe a chemical reaction, ensuring that the quantities and types of atoms are balanced on both sides of the equation.

molecules

Molecules are groups of two or more atoms bonded together. They are the smallest units of a chemical compound that can exist. In a chemical equation, molecules are represented by their chemical formulas, which show the types and numbers of atoms involved.
Let's take water (\(H_2O\)) as an example:

• The formula \(H_2O\) indicates that each molecule of water consists of 2 hydrogen (H) atoms and 1 oxygen (O) atom.
• In an equation, the coefficient before the formula tells us how many molecules of that substance are involved in the reaction.

So, in the equation \(2H_2 + O_2 \rightarrow 2H_2O\), the '2' in front of \(H_2O\) means there are 2 water molecules, which combined have 4 hydrogen atoms and 2 oxygen atoms. Every molecule seen in a chemical equation follows the rules of chemistry, ensuring that atoms are neither created nor destroyed during a reaction.

law of conservation of mass

The law of conservation of mass is a fundamental principle in chemistry, stating that mass is neither created nor destroyed in a chemical reaction. This means that the total mass of the reactants must equal the total mass of the products.
In a chemical equation, this law is reflected by the need to balance the equation. This means ensuring that the number of each type of atom on the reactant side is equal to the number of each type on the product side.
For example, in the equation \(2H_2 + O_2 \rightarrow 2H_2O\):

• We start with 4 hydrogen atoms (from \(2H_2\)) and 2 oxygen atoms.
• On the product side, we have 4 hydrogen atoms and 2 oxygen atoms in 2 molecules of \(H_2O\).

This balance demonstrates the law of conservation of mass, as the total number of each type of atom remains consistent before and after the reaction.
This law is crucial for understanding chemical reactions and ensuring that chemical equations are correctly balanced.