It is always advisable to purchase the most diluted acid possible suitable for your specific needs, both for safety reasons and to facilitate its use. However, it is sometimes necessary to further dilute. Do not neglect protective equipment, as concentrated acids can cause severe chemical burns. When calculating the quantities of water and acid to mix, you need to know the initial molar concentration of the acid and that of the solution you want to obtain.
Steps
Part 1 of 3: Calculate the Dilution Formula
Step 1. Check your current concentration
Read the label on the acid package or find the concentration in the data provided by the chemistry problem. This value is often expressed as "molarity" or "molar concentration", abbreviated to "M". For example, a "6 M" product contains 6 moles of acid molecules per liter. Indicates the initial concentration with: C.1.
The formula described below also uses the term V.1. This is the volume of the acid that will be added to the water. You probably won't be using all of the acid pack, so you may not know this exactly yet.
Step 2. Decide the result
In general, both the final concentration to be obtained and the volume of acid are indicated in the school problem or in the laboratory test. For example, it may be necessary to produce half a liter of diluted acid to a concentration of 2 M. You can indicate the desired concentration with C.2 and the desired volume with V.2.
- If you are using odd units of measurement, convert them all to molar concentration (moles per liter) and liters before proceeding.
- If you don't know the final concentration and volume data, ask your teacher, chemist or an expert on the work you need to do with acid for more information.
Step 3. Write the formula to calculate the dilution
Whenever you are preparing to dilute a solution, you must use this formula: C.1V.1 = C2V.2. Translated into words, the equation states that "the product of the initial concentration of the solution and its volume is equal to the product of the concentration of the diluted solution and its volume". You know that this equality is true because the product of concentration and volume gives the total amount of acid and this does not vary regardless of the amount of water added.
In the example considered you can write: (6 M) (V1) = (2 M) (0, 5 l).
Step 4. Solve the equation for V.1.
The term V1 indicates how much acid you need to put in the water to get the desired concentration and volume. Rewrite the formula as V.1= (C2V.2) / (C1) and then enter the known numbers inside it.
In the example considered you will have: V1= [(2 M) (0, 5 l)] / (6 M) = 1/6 l = 0, 167 l, i.e. 167 ml.
Step 5. Calculate the volume of water needed
Now that you know the value of V.1, the amount of acid you need to use, and V.2, the total volume of the solution, you can easily calculate the amount of water by difference. V.2 - V1 = volume of water needed.
In the case considered, you will get 0, 5 l of solution in which there are 0, 167 l of acid. The volume of water required for dilution is: 0.5 l - 0.17 l = 0.33 l, or 333 ml
Part 2 of 3: Prepare a Safe Workspace
Step 1. Read the safety data sheets on the internet
These offer detailed but concise information about the product you are handling. Search by entering the exact name of the acid you intend to use, such as "hydrochloric acid", in the online database. Some acids must be handled with special safety precautions, in addition to those indicated below.
- Sometimes you have to refer to multiple safety data sheets, based on the concentration of the acid and the other substances you intend to add. Choose the one that best suits your initial solution.
- If you prefer, you can also use this database.
Step 2. Wear a certified chemical hazard mask and lab coat
A mask protects the eyes on all sides and is essential when using acids. To avoid contact of the solution with the skin, also wear gloves and a lab coat or apron.
- If you have long hair, tie it up before you start.
- An acid can also take hours to corrode a fabric and punch a hole in the dress. While you may not notice any splashes, be aware that a few drops of the substance can damage clothes if they are not covered by a gown.
Step 3. Work under a fume hood or in a well-ventilated area
Whenever possible, keep the acid solution under a lit fume hood while you work. This way you limit your exposure to the vapors produced by the chemical, which can be corrosive or poisonous. If you don't have a hood available, open all windows and doors, or turn on a fan to ensure adequate airflow.
Step 4. Locate a source of running water
If acid splashes into your eyes or skin, you should wash the area with cold running water for 15-20 minutes. Do not begin the dilution process until you are satisfied that the closest sink or eyewash station is functional.
When washing your eyes, try to keep your eyelids as open as possible. Rotate the eyeball in all directions to make sure the entire surface is rinsed
Step 5. Organize a specific action plan for the acid you are using to deal with any splashes and spills
You can purchase a special kit that contains all the necessary material, or buy the neutralizer and absorbent material separately. The process described below is suitable for hydrochloric, sulfuric, nitric and phosphoric acids, while other compounds may require different handling. For that reason, do all the necessary research on proper disposal.
- Air the room by opening doors and windows, or by turning on a fan or extractor hood.
- Apply a weak base, such as sodium carbonate, baking soda, or calcium carbonate, to the edges of the acid drop. This modus operandi allows you to avoid further splashing.
- Continue to slowly sprinkle the weak base on the acid by slowly moving inward to the stain until it is completely covered.
- Mix everything with a plastic tool. Check the pH of the spill with litmus paper. Add more base to raise the pH to a value between 6 and 8 and finally flush the compound down the drain using plenty of water.
Part 3 of 3: Dilute the Acid
Step 1. When using concentrated acids, cool the water in an ice bath
This step is only necessary if you are using extremely concentrated acid solutions, such as sulfuric acid at 18 M or hydrochloric acid at 12 M. To keep the water temperature low, surround the container that contains it with ice before dilution. at least 20 minutes.
In most cases, however, water at room temperature is safe
Step 2. Pour distilled water into a large flask
For procedures where precise dosages are very important, such as titration, the use of a flask is essential. For other types of practical projects, a flask is more than enough. Either way, choose a container that is large enough for the amount of solution you want to make, making sure there is enough empty space to avoid overflowing.
It is not necessary to accurately measure the quantity of distilled water if it comes from another container in which it has been carefully pre-dosed
Step 3. Add a small amount of acid
If you need to dilute small doses of acid, you can use a graduated pipette (called Mohr's) or a volumetric pipette with a rubber bulb. For larger volumes, insert a funnel into the opening of the flask and slowly pour in a small amount of acid using a graduated cylinder.
Never use mouth pipettes in a chemistry lab
Step 4. Wait for the solution to cool
Strong acids can generate a lot of heat when added to water. If the element is highly concentrated, the solution may also create corrosive splashes and fumes. If this happens, you need to go through the entire dilution process by adding very small amounts of acid, or chill the water in an ice bath before continuing.
Step 5. Continue to pour in the rest of the acid, always a little at a time
Each time let the solution cool, especially if you notice a lot of heat, smoke, or splash. Do this until you have diluted all the acid.
The volume of the acid was calculated as term V.1 according to the data in the first section of the article.
Step 6. Mix the solution
For best results, you need to mix it with a glass stick after each dose of acid. If the size of the flask makes this step impossible, then mix the solution at the end of the dilution and after removing the funnel.
Step 7. Put the acid back and rinse the tools
Pour the newly created solution into an unambiguously labeled container, preferably a PVC-lined glass bottle, and store it in a safe place. Rinse the flask, funnel, glass stick, pipette and / or graduated cylinder with water to remove all traces of acid.
Advice
- Always add acid to the water and not vice versa. When the two substances mix, they easily create a lot of heat. The greater the amount of water, the greater the "material" at your disposal to dissipate and absorb heat. This will prevent the mixture from boiling and splashing.
- To remind you of this important detail, memorize the acronym ASA: "Always Add Acid".
- When mixing two acids, always add the stronger one to the weaker one for the reasons stated above.
- You can use half of the water you need, dilute the acid and then slowly add the rest of the water. This method is not recommended for concentrated solutions.
- Buy the most diluted acid possible that meets your needs, to ensure maximum safety and avoid storage problems.
Warnings
- Even when the acid's effects are not severe, be aware that this may still be poisonous. For example, hydrogen cyanide is not strong, but extremely toxic.
- Never try to neutralize the effects of acid splashes with a strong base such as potassium hydroxide (KOH) or sodium hydroxide (NaOH). Instead, choose water or a weak base such as diluted baking soda (NaHCO3).
- Don't melt the materials for fun or other reasons unless you know exactly what you are doing. You could create extremely dangerous products such as toxic or explosive gases that can self-ignite.
- What are called "weak" acids can produce a lot of heat and be very dangerous. The distinction between strong and weak acids is a pure chemical classification.
