Dilution is the process by which a concentrated solution is made less concentrated. There are many reasons for wanting to dilute, from the most serious to the most random. For example, biochemists dilute solutions from their concentrated form to create new solutions for use in their own experiments, while, completely on the other hand, bartenders often dilute liquors with light drinks or juice to create quieter cocktails. The appropriate formula for calculating a dilution is C.1V.1 = C2V.2, where C1 and C2 represent the respective concentrations of the initial and final solutions, and V.1 and V2 represents their volumes.
Steps
Method 1 of 2: Thoroughly Dilute Concentrates via the Dilution Equation
Step 1. Determine what you "know and don't know"
Doing a dilution in chemistry often means taking a small dose of solution of which you know the concentration, and then adding a neutral liquid (such as water) to create a new solution with a larger volume, but at a lower concentration. This procedure is carried out very frequently in chemical laboratories where, for reasons of efficiency, the reagents are often stored at high concentrations, which are then diluted to be used in the various experiments. Usually, in most real-world situations, you will surely know both the concentration of your starting solution and the concentration and volume you want to get in the second solution, but not the "volume of the first solution you need to get it".
- However, in other situations (especially in school practice problems), you may need to find other pieces of the puzzle - for example, you may be given initial focus and volume, and you may be prompted to find final focus if you dilute the solution at a given volume. For any dilution, it is important to note the known and unknown variables before starting.
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Let's consider an example problem. Let's say we are asked to dilute a 5M solution with water to get 1 liter of 1 "mM" solution. In this case, we know the concentration of the starting solution and the volume and concentration that we want to obtain, but not the amount of the starting solution to which we have to add the water to obtain them.
Remember: in chemistry M is a measure of concentration called "molarity", which indicates the moles of a substance per liter
Step 2. Enter your values into formula C1V.1 = C2V.2.
In this formula, C.1 indicates the concentration of the starting solution, V.1 indicates its volume, C.2 indicates the concentration of the final solution, and V.2 indicates its volume. Insert the known values into this equation - it should allow you to derive the unknown value with little difficulty.
- It may be helpful to put a question mark in front of the unit you want to determine to help you solve the equation.
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Let's continue our example. We will enter our known values as follows:
- C.1V.1 = C2V.2
- (5 M) V1 = (1 mM) (1 L). Our two concentrations have different units. Let's stop here and move on to the next step.
Dilute Solutions Step 3 Step 3. Let's take into consideration the differences in the units of measurement
Since dilutions predict changes in concentration (which can sometimes be substantial), it is not uncommon for two variables in your equation to be expressed in different units. While this problem is often overlooked, the mismatched units in your equation can lead to you getting staggered results, even by several orders of magnitude. Before solving, convert all values to the same unit of measurement.
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In our example, we have several units for concentration: M (molar) and mM (millimolar). Let's convert the second measure to M:
- 1mM × 1M / 1000mM
- = 0.001 M
Dilute Solutions Step 4 Step 4. Solve
When all units match, solve your equation. It can usually be done with simple algebra.
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We left our problem at this point: (5 M) V1 = (1 mM) (1 L). We solve for V.1 with the new units of measurement.
- (5 M) V1 = (0, 001 M) (1 L)
- V.1 = (0, 001 M) (1 L) / (5 M).
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V.1 = 0., 0002 L., or 0.2 mL.
Dilute Solutions Step 5 Step 5. Learn how to use your answers in a practical way
Let's say you've found your missing value, but aren't sure how to apply this new information in a dilution you need to make in the real world. This is understandable: the language of mathematics and science sometimes does not lend itself to concrete situations. When you know all four values in equation C.1V.1 = C2V.2, perform the dilution as follows:
- Measure the volume V1 of the solution with concentration C.1. Then, add enough thinner (water or otherwise) to create a total volume V.2. This new solution will have the desired concentration (C.2).
- In our example, we will first need to measure 0.2 mL from our 5 M solution. Next, we will need to add enough water to increase the volume of the solution up to 1 L: 1 L - 0, 0002 L = 0, 9998 L, or 999, 8 mL. In other words, we will need to add 999.8 mL of water to our small solution sample. Our new diluted solution will have a concentration of 1mM, which was just what we wanted to achieve from the start.
Method 2 of 2: Make Simple and Practical Dilutions
Dilute Solutions Step 6 Step 1. Read each package for information
There are tons of reasons why you might want to dilute at home, in the kitchen, or in other places outside of chemical laboratories. For example, simply making orange juice from a concentrate is a dilution. In many cases, the products that need to be diluted carry the information necessary for dilution on the packaging. They might even include precise instructions to follow. Here are some things to check when looking for information:
- The volume of the product to be used
- The volume of diluent to be used
- The type of thinner to use (usually water)
- Special mixing instructions
- There will probably be no indication on the precise concentration of liquids to be used (this information is generally superfluous for the consumer).
Dilute Solutions Step 7 Step 2. Add the diluent to the concentrated solution
For simple home dilutions, such as those you might prepare in the kitchen, you will only need to know before you begin the volume of concentrate you are using, and the approximate final concentration you need. Dilute the concentrate with the right amount of diluent, which can be determined based on the initial volume of the concentrate.
- For example, if we want to dilute a 1/4 cup of concentrated orange juice by 1/4, we will use "3 cups" of concentrated water. Our final blend will have 1 cup of concentrate out of a total of 4 cups of liquid - 1/4 of its initial concentration.
- Now, a more complex example: if we want to dilute "2/3 cup" of concentrate to 1/4 of its initial concentration, we need to add 2 cups of water, since 2/3 of a cup correspond to 1/4 of 2 & 2 / 3 cups of total liquid.
- Make sure you pour your substances into a container large enough to hold the final volume you want to achieve (such as a large bowl or similar container).
Dilute Solutions Step 8 Step 3. Ignore the volume of powders in most cases
Adding powdered substances (such as some drink mixes) to liquids usually should not be considered as a dilution. The change in volume of a liquid, obtained by adding a small amount of powder, is usually so small that it can be safely ignored. In other words, when you add small amounts of powder to a liquid, simply add it to the final volume of liquid you want to get, and mix it all together.
Warnings
- Follow any safety instructions provided by the manufacturing company, or required by your company. This is especially important if you need to dilute acid-based solutions.
- Working with an acid solution may require more detailed steps and more safety procedures than diluting non-acid solutions.
