Why is concentration important chemistry

Serial dilutions involve diluting a stock or standard solution multiple times in a row. Typically, the dilution factor remains constant for each dilution, resulting in an exponential decrease in concentration. For example, a ten-fold serial dilution could result in the following concentrations: 1 M, 0. As is evidenced in this example, the concentration is reduced by a factor of ten in each step. Serial dilutions are used to accurately create extremely diluted solutions, as well as solutions for experiments that require a concentration curve with an exponential or logarithmic scale.

Serial dilutions are widely used in experimental sciences, including biochemistry, pharmacology, microbiology, and physics. Molarity is a unit of concentration; it is equal to moles of solute divided by the total volume of the solution in liters. In chemistry, molar concentration, or molarity, is defined as moles of solute per total liters of solution.

This is an important distinction; the volume in the definition of molarity refers to the volume of the solution , and not the volume of the solvent. The reason for this is because one liter of solution usually contains either slightly more or slightly less than 1 liter of solvent, due to the presence of the solute.

It is important to distinguish moles from molarity; molarity is a measurement of concentration while moles are a measure of the amount of substance present at a given time.

Molarity : Molarity is a measurement of concentration, with units of mol solute per liter solution. Molarity can be used in a various calculations involving solutions. The following formula is very useful, as it relates the molarity of the solution, the total volume of the solution in liters , and the number of moles solute:. A student pipettes a mL sample of a 1. How many moles of potassium bromide are contained in the sample?

You might notice that the above formula bears some resemblance to our dilution formula:. After all, in any dilution, what changes is the amount of solvent, while the number of moles of solute remains constant throughout. Molarity Practice Problems — YouTube : This video demonstrates practice problems with molarity, calculating the moles and liters to find the molar concentration.

All rights reserved. See more Encyclopedia articles on: Chemistry: General. Enter your search terms:. The concentration of a solute is very important in studying chemical reactions because it determines how often molecules collide in solution and thus indirectly determines the rates of reactions and the conditions at equilibrium see chemical equilibrium.

These terms are widely employed to express the amounts of trace pollutants in the environment. It is sometimes convenient to base concentration on a fixed volume, either of the solution itself, or of the solvent alone. The latter distinction is important because volumes of mixed substances are not strictly additive. This is the method most used by chemists to express concentration, and it is the one most important for you to master.

Molar concentration molarity is the number of moles of solute per liter of solution. The important point to remember is that the volume of the solution is different from the volume of the solvent ; the latter quantity can be found from the molarity only if the densities of both the solution and of the pure solvent are known. Similarly, calculation of the weight-percentage concentration from the molarity requires density information; you are expected to be able to carry out these kinds of calculations, which are covered in most texts.

A 1-molal solution contains one mole of solute per 1 kg of solvent. Molality is a hybrid concentration unit, retaining the convenience of mole measure for the solute, but expressing it in relation to a temperature-independent mass rather than a volume. Molality, like mole fraction, is used in applications dealing with certain physical properties of solutions; we will see some of these in the next lesson.

Anyone doing practical chemistry must be able to convert one kind of concentration measure into another. This is because the number of moles of the solute does not change, but the total volume of the solution increases.

We can set up an equality between the moles of the solute before the dilution 1 and the moles of the solute after the dilution 2. Since the moles of solute in a solution is equal to the molarity multiplied by the volume in liters, we can set those equal. Finally, because the two sides of the equation are set equal to one another, the volume can be in any units we choose, as long as that unit is the same on both sides.

Our equation for calculating the molarity of a diluted solution becomes:. The solution has been diluted by a factor of five, since the new volume is five times as great as the original volume. Consequently, the molarity is one-fifth of its original value. Another common dilution problem involves deciding how much a highly concentrated solution is required to make a desired quantity of solution with a lower concentration.

The highly concentrated solution is typically referred to as the stock solution. Concentration is important in healthcare because it is used in so many ways. It's also critical to use units with any values to ensure the correct dosage of medications or report levels of substances in blood, to name just two. Another way of looking at concentration such as in IV solutions and blood is in terms of equivalents. One equivalent is equal to one mole of charge in an ion.

The value of the equivalents is always positive regardless of the charge. Equivalents are used because the concentration of the charges is important than the identity of the solutes. For example, a standard IV solution does not contain the same solutes as blood but the concentration of charges is the same.

What mass of sodium did the patient receive?