Question

Apply How does a chemist count the number of particles in a given number of moles of a substance?

Short answer

To count the number of particles in a given number of moles of a substance, a chemist applies Avogadro's constant, which is approximately \(6.022 \times 10^{23}\) particles per mole. The number of particles can be determined using the equation: Number of particles = (Number of moles) × \(N_A\), where "Number of particles" is the total number of atoms, molecules, ions, or other entities in the substance, "Number of moles" is the given amount of the substance in moles, and \(N_A\) is Avogadro's constant.

Step-by-step solution

Understand the mole concept

A mole is a unit used in chemistry to express amounts or quantities of a substance. It is defined as the amount of a substance that contains as many particles (atoms, molecules, ions, or other entities) as there are in 12 grams of carbon-12.

Learn about Avogadro's constant

Avogadro's constant, denoted \(N_A\), is the number of particles (atoms, molecules, or other entities) in one mole of any substance. It has a value of approximately \(6.022 \times 10^{23}\) particles per mole. This constant is named after the Italian scientist Amedeo Avogadro.

Use Avogadro's constant to count particles

To determine the number of particles in a given number of moles of a substance, you can use the following equation: Number of particles = (Number of moles) × \(N_A\) where "Number of particles" is the total number of atoms, molecules, ions, or other entities in the substance; "Number of moles" is the given amount of the substance in moles, and \(N_A\) is Avogadro's constant.

Example calculation

Let's calculate the number of particles in 2 moles of water (H₂O). Here, the number of moles is 2. We can use the equation in Step 3 to find the number of particles: Number of particles = (Number of moles) × \(N_A\) Number of particles = (2) × \(6.022 \times 10^{23}\) Number of particles = \(1.204 \times 10^{24}\) So, there are \(1.204 \times 10^{24}\) particles, which in this case are water molecules, in 2 moles of water.

Key concepts

Avogadro's constant

Named after the Italian scientist Amedeo Avogadro, Avogadro's constant is a crucial concept in chemistry. It provides a link between the macroscopic world we can see and the microscopic world of atoms and molecules. The constant is denoted by the symbol \( N_A \) and is approximately equal to \( 6.022 \times 10^{23} \) particles per mole. This means that in one mole of any substance, there are \( 6.022 \times 10^{23} \) atoms, molecules, ions, or other particles.

Understanding Avogadro's constant is fundamental, as it helps us relate quantities in the lab to numbers of particles that are far too small to count directly. For example, one mole of water molecules contains the same number of molecules as one mole of sodium or any other substance, even though their individual masses are different.

Particles in chemistry

In chemistry, when we refer to "particles," we are talking about the smallest units that make up a substance. These particles can be atoms, molecules, ions, or sometimes even larger entities like proteins or entire cells, depending on the context. Understanding what kind of particles make up your substance is essential to correctly using the mole concept.

- **Atoms:** The basic units of matter and the defining structure of elements. - **Molecules:** Formed when two or more atoms are chemically bonded together. - **Ions:** Atoms or molecules that have gained or lost one or more of their electrons, resulting in a charge. Knowing the type of particles present is crucial when performing calculations such as finding out the number of particles in a given number of moles. This understanding helps in making accurate stoichiometric calculations in chemical reactions.

Moles and particles conversion

Converting between moles and the number of particles involves using Avogadro's constant. This conversion is a fundamental part of chemical calculations and is generally straightforward once you understand the basic relationship. Here's how to do it:

- Calculate the number of particles by multiplying the number of moles by Avogadro's constant: \[ \text{Number of particles} = \text{Number of moles} \times N_A \]- For example, to find out how many water molecules are in 2 moles of water, use the equation: \[ \text{Number of particles} = 2 \times 6.022 \times 10^{23} = 1.204 \times 10^{24} \]- Therefore, 2 moles of water contain \( 1.204 \times 10^{24} \) molecules of water.

This conversion is key for quantitative analysis in chemistry, allowing us to determine the proportions of substances needed in reactions, quantities of products formed, or even to analyze the composition of a sample.