How to Make Up Concentrations of HCL Levels in Chemistry
You can make hydrochloric acid (HCl) solutions by diluting a highly concentrated solution of the acid. Concentrated acid usually has a concentration of 12 molar (abbreviated 12 M), which means that there are 12 moles of HCl molecules in each liter of acid. A mole is a unit used in chemistry to describe a set number of 6.02 x 10^23 atoms or molecules. To make your solution, dilute a known volume of concentrated acid in water to a precise final volume.
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Things You'll Need
- Concentrated hydrochloric acid (HCl) 12 molar
- Pipette and bulb
- Volumetric flasks
- Calculator
Instructions
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Determine the concentration of HCl required in your diluted solution and the volume you wish to make. For example, you might want to make 2 liters (L) of a 0.30 molar (M) solution, meaning you will have 0.30 moles of HCl in every liter of your solution.
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Calculate the volume of concentrated acid you require. To do this, you will use the following calculation: V1 = (C2 x V2)/C1. V1 is the volume of the concentrated acid you need, C1 is the molarity of that acid, V2 is the volume of dilute acid you want and C2 is the concentration of that dilute acid. C1 and C2 must be in the same units and also V1 and V2. In the the example, you would need V1 = (0.30 x 2)/12 = 0.05 L of 12 M acid.
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Fill 2/3 of volumetric flask with water.
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Place a bottle of concentrated HCl in a fume hood and open the cap.
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Use a pipette of the appropriate size and fitted with a bulb to draw up the required volume of the concentrated acid. For the example, use a 50 milliliter (mL) pipette. If your required volume does not correspond to a common pipette size, you might need to perform this transfer in stages, using a few different pipettes. For instance, if you required 35 mL, you might make one transfer using a 25 mL pipette and another using a 10 mL pipette.
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Place the tip of the full pipette in the volumetric flask just above the surface of the water and slowly and carefully release the seal on the pipette bulb to allow the acid to drain into the water. The water may become extremely hot as you add more acid, so take your time and monitor the solution temperature by feeling the exterior of the flask. Pause and gently swirl the base of the flask several times when adding the acid.
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Remove the empty pipette and place it in a safe location where it can later be rinsed out and cleaned. Be cautious of any HCl that may run out of the pipette. Recap the bottle of concentrated acid.
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Swirl the flask and monitor its temperature. Do this gently. Allow the flask and contents to cool to room temperature.
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Add more water until the solution level in the flask exactly matches the volumetric mark on the neck. Stopper the flask and slowly swirl and invert a few times (holding the stopper in place) to completely mix the diluted solution.
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Tips & Warnings
The upper surface of water in the neck of a volumetric flask will form a slight downward curve (a meniscus). You will want to align the lowest portion of this curve with the volume mark on the flask neck.
Use pure water, such as distilled or deionized.
Both concentrated and dilute HCl are extremely hazardous. HCl is corrosive to skin and many other materials, such as metals. Only attempt this procedure if you have the education and training to safely handle strong acids.
Read the material safety data sheet for HCl before using.
HCl can give off corrosive vapors. Perform this entire procedure in a chemical fume hood.
Wear appropriate safety equipment such as lab coat, acid-resistant gloves and safety goggles.
Dispose of any waste acid appropriately in a suitable container.
Label all glassware and other containers to identify their contents.
Always add acid to the majority of the required water, never add water to acid. Adding acid to water allows the substantial heat of diluting the acid to better dissipate.
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