Ammonium acetate is a white crystalline salt prepared by mixing ammonia and acetic acid, better known as vinegar. This salt finds use as a buffer chemical for some experiments in biology and chemistry labs. It smells faintly of vinegar and is relatively easy to make; just be sure that the vinegar and ammonia you buy don't contain other chemicals because these could contaminate your end product. Ammonium acetate isn't an especially dangerous chemical, but as with anything else you should make sure you store it out of reach of children.
- Skill level:
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Things you need
- Beaker (or other glass container)
- Graduated cylinder (or other volume-measuring device)
- pH paper
- Stir rod
Determine the concentration of the acetic acid in your vinegar and of the ammonia in your ammonia solution. Most store-bought ammonia and vinegar will list concentrations as per cent weight per volume, which gives you the number of grams per 100ml of solution. Vinegar may be in per cent by volume, which gives you the number of millilitres of acetic acid per 100ml of solution.
If the concentration is per cent weight, then replace the per cent sign with grams and do the following:
For ammonia: Divide by 17.031 and multiply by 10 to get the number of moles of ammonia per litre of solution.
Example: A 5 per cent ammonia solution contains 5 grams of ammonia per 100ml of product. 5 / 17.031 = 0.294 x 10 = 2.9 moles per litre.
For vinegar: Divide by 60.05 and multiply by 10 to get the number of moles of acetic acid per litre of solution.
Example: A 5 per cent by mass vinegar solution contains 5 grams of acetic acid per 100ml of vinegar. 5 / 60.05 = 0.0833 x 10 = 0.833 moles per litre.
Ammonia will typically be by per cent weight. If the concentration of vinegar is specified in per cent by volume, change the per cent sign to ml and multiply it by 1.049 grams, then divide by 60.05 and multiply by 10 to get the number of moles per litre.
Example: A 5 per cent by volume solution contains 5ml of acetic acid per 100ml of vinegar.
5ml x 1.049 grams per mL = 5.25 grams
5.25 / 60.05 = 0.0873 moles per 100ml
0.0873 x 10 = 0.873 moles per litre
Divide 0.5 by the number of moles per litre of ammonia. This gives you the number of litres of ammonia solution that will contain 0.5 moles of ammonia. The goal here is to measure out enough of each reactant to make 0.5 moles of product.
Example: 0.5 / 2.9 = 0.172 litres or 172 millilitres of ammonia.
Divide 0.5 by the number of moles per litre of vinegar. This gives you the number of litres of vinegar that will contain 0.5 moles of acetic acid.
Example: 0.5 / 0.833 = 0.60 litres or 600 millilitres.
Put on your goggles. Using a graduated cylinder, measure out the amount of ammonia you calculated into the glass container; in the example, this was 172ml of ammonia. Make sure you do this in a well-ventilated area.
Measure the amount of vinegar you calculated. In the example it was 600ml of vinegar. Add the vinegar slowly to the ammonia. Stir the solution gently.
Test the pH of the solution with pH paper. It should be close to pH 7. If the pH is 8 or above, add a little more vinegar and retest pH. If it is 6 or below, add a little more ammonia and retest pH.
Tips and warnings
- Ammonia is a weak base while vinegar is a weak acid. When mixed in equal proportions (1 mole to 1 mole), they make a neutral salt. If the proportions are identical, the resulting solution should be neutral in pH; a pH above or below 7 indicates some acid/base remains unneutralized.
- Do not attempt to make ammonium acetate this way if the ammonia or vinegar products you are using contain other chemicals. Some window cleaners, for example, contain ammonia but also contain many other chemicals that could participate in other reactions, so you will not get the results you expect.
- Always be careful when working with acids and bases; make sure you do not get ammonia or vinegar in your eyes, where they could cause irritation or even serious damage.
- Do not attempt to drink or consume the solution of ammonium acetate you have prepared; ammonium acetate prepared in this way is not meant for human consumption.
- Do not mix this product with bleach or strong acids.
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