specify concentration. Usage the state concentrated and dilute to explain the relative concentration of a solution. Calculation the molarity the a solution. Calculate portion concentration (m/m, v/v, m/v). Define a systems whose concentration is in ( extppm) or ( extppb). Usage concentration systems in calculations. Identify equivalents for an ion. Complete calculations relating equivalents to moles, volumes, or mass. Complete dilution calculations.

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There room several means to refer the amount of solute present in a solution. The concentration that a solution is a measure up of the quantity of solute that has actually been dissolved in a given amount of solvent or solution. A concentrated solution is one that has a relatively huge amount of dissolved solute. A dilute solution is one that has actually a relatively small amount of liquified solute. However, these terms are relative, and we need to be able to express concentration in a much more exact, quantitative manner. Still, concentrated and also dilute are helpful as terms to to compare one equipment to one more (see figure below). Also, be conscious that the terms "concentrate" and "dilute" deserve to be supplied as verbs. If you were to warmth a solution, leading to the solvent to evaporate, you would be concentrating it, because the proportion of solute come solvent would certainly be increasing. If you were to add an ext water to an aqueous solution, you would certainly be diluting it since the ratio of solute come solvent would certainly be decreasing.

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Figure (PageIndex1): remedies of a red dye in water indigenous the many dilute (on the left) to the most focused (on the right).

Percent Concentration

One means to explain the concentration of a solution is through the percent that the solution that is written of the solute. This percentage have the right to be figured out in among three ways: (1) the fixed of the solute divided by the mass of solution, (2) the volume of the solute divided by the volume of the solution, or (3) the fixed of the solute split by the volume the the solution. Due to the fact that these techniques generally result in slightly different vales, it is important to constantly indicate exactly how a offered percentage was calculated.



Volume Percent

The percent of solute in a systems can more easily be identified by volume when the solute and also solvent room both liquids. The volume the the solute separated by the volume that the equipment expressed as a percent, yields the percent through volume (volume/volume) that the solution. If a systems is make by taking (40. : extmL) the ethanol and adding enough water to do (240. : extmL) of solution, the percent by volume is:

<eginalign extPercent by volume &= frac extvolume of solute extvolume of solution imes 100\% \ &= frac40 : extmL ethanol240 : extmL solution imes 100\% \ &= 16.7\% : extethanol endalign>

Frequently, ingredient brand on food products and also medicines have amounts detailed as percentages (see figure below).

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Figure (PageIndex2): Hydrogen peroxide is frequently sold together a (3\%) by volume solution for use as a disinfectant.

It should be provided that, unlike in the instance of mass, you cannot simply include together the volumes of solute and solvent to gain the last solution volume. When adding a solute and also solvent together, mass is conserved, however volume is not. In the instance above, a solution was make by beginning with (40 : extmL) that ethanol and adding enough water to make (240 : extmL) of solution. Merely mixing (40 : extmL) that ethanol and (200 : extmL) that water would not offer you the same result, as the last volume would most likely not be precisely (240 : extmL).

The mass-volume percent is additionally used in part cases and also is calculate in a similar means to the previous two percentages. The mass/volume percent is calculate by dividing the fixed of the solute through the volume the the solution and also expressing the result as a percent.

For example, if a systems is all set from (10 : ceNaCl) in sufficient water to make a (150 : extmL) solution, the mass-volume concentration is

<eginalign extMass-volume concentration & frac extmass solute extvolume solution imes 100\% \ &= frac10 : extg : ceNaCl150 : extmL solution imes 100\% \ &= 6.7\% endalign>




Molarity

snucongo.orgists primarily need the concentration of solutions to it is in expressed in a means that accounts because that the variety of particles present that can react follow to a details snucongo.orgical equation. Due to the fact that percentage measurements are based upon either mass or volume, they are generally not advantageous for snucongo.orgical reactions. A concentration unit based upon moles is preferable. The molarity (left( extM ight)) of a equipment is the variety of moles the solute liquified in one liter that solution. To calculate the molarity of a solution, you division the mole of solute through the volume that the equipment expressed in liters.

< extMolarity : left( extM ight) = frac extmoles that solute extliters that solution = frac extmol extL>

Note that the volume is in liters of solution and not liters that solvent. When a molarity is reported, the unit is the price ( extM), i m sorry is check out as "molar". For example, a equipment labeled together (1.5 : extM : ceNH_3) is a "1.5 molar systems of ammonia".


Example (PageIndex1)

A systems is all set by dissolve (42.23 : extg) that (ceNH_4Cl) into sufficient water to make (500.0 : extmL) that solution. Calculation its molarity.

Solution

Step 1: perform the well-known quantities and also plan the problem.

Known

fixed of (ceNH_4Cl = 42.23 : extg) Molar massive of (ceNH_4Cl = 53.50 : extg/mol) Volume of solution (= 500.0 : extmL = 0.5000 : extL)

Unknown

Molarity (= ? : extM)

The massive of the ammonium chloride is an initial converted come moles. Then, the molarity is calculated by separating by liters. Keep in mind that the provided volume has been converted to liters.

Step 2: Solve.

<42.23 : extg : ceNH_4Cl imes frac1 : extmol : ceNH_4Cl53.50 : extg : ceNH_4Cl = 0.7893 : extmol : ceNH_4Cl>

Step 3: Think about your result.

The molarity is (1.579 : extM), definition that a liter that the solution would save 1.579 mole of (ceNH_4Cl). Having four significant figures is appropriate.


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Figure (PageIndex3): Volumetric flasks come in many sizes, each designed come prepare a different volume the solution.

Dilutions

When extr water is added to one aqueous solution, the concentration that that systems decreases. This is since the variety of moles that the solute does no change, yet the total volume of the equipment increases. Us can set up an equality in between the mole of the solute prior to the dilution (1) and the moles of the solute after ~ the dilution (2).

< extmol_1 = extmol_2>

Since the mole of solute in a systems is equal to the molarity multiply by the volume in liters, we can collection those equal.

Finally, due to the fact that the 2 sides of the equation are collection equal come one another, the volume deserve to be in any kind of units us choose, as lengthy as the unit is the very same on both sides. Our equation because that calculating the molarity that a diluted equipment becomes:

Additionally, the concentration have the right to be in any type of other unit as long as (M_1) and (M_2) space in the very same unit.

Suppose that you have actually (100. : extmL) that a (2.0 : extM) solution of (ceHCl). Girlfriend dilute the systems by including enough water to do the systems volume (500. : extmL). The new molarity can easily be calculation by utilizing the over equation and also solving for (M_2).

The solution has been diluted through a variable of five, since the new volume is five times as great as the original volume. Consequently, the molarity is one-fifth the its original value. Another common dilution problem involves deciding how much a highly concentrated solution is forced to make a desired quantity of solution with a lower concentration. The highly focused solution is generally referred to as the stock solution.



Equivalents

Concentration is necessary in healthcare because it is supplied in so numerous ways. It"s also an essential to use units with any kind of values to ensure the exactly dosage of medications or report levels of building material in blood, to name just two.

Another method of looking at concentration such together in IV solutions and blood is in regards to equivalents. One tantamount is equal to one mole of charge in one ion. The value of the equivalents is always positive nevertheless of the charge. Because that example, (ceNa^+) and also (ceCl^-) both have actually 1 indistinguishable per mole.

<eginarrayll extbfIon & extbfEquivalents \ ceNa^+ & 1 \ ceMg^2+ & 2 \ ceAl^3+ & 3 \ ceCl^- & 1 \ ceNO_3^- & 1 \ ceSO_4^2- & 2 endarray>

Equivalents room used because the concentration of the charges is essential than the identity of the solutes. Because that example, a standard IV equipment does not contain the very same solutes together blood yet the concentration of charges is the same.

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Sometimes, the concentration is reduced in which case milliequivalents (left( extmEq ight)) is a more appropriate unit. Similar to metric prefixes offered with base units, milli is offered to change equivalents for this reason (1 : extEq = 1000 : extmEq).