Intro: Determining an Ion Concentration Using Solubility
in chemistry many types of elements dissolve in water. Many of these elements can be harmful, and quantifying how much of these elements is in some water supplies is important. For this info graphic I will teach how to determin dissolved silver levels in water.
Step 1: How to Set Up
silver it's self as an ion dissolves in water in most cases, unless an ionic reaction occurs with another element to make it insoluble in water. Some elements when combined with others form a cloudy precipitate which can be filtered and measured. For this experiment you will need a water supply with an unknown silver concentration dissolved. For this experiment we will add our own. 1 gram of silver nitrate (AgNO3) can be dissolved in water. This ion is soluble.
Step 2: Making Your Precipitating Solution
In order to precipitate silver, it must be bound to an element that makes it undissolvable. A look at solubility chart available in all libraries, will show silver chloride (AgCl) will not dissolve in water. The reaction is shown above.
Step 3: Precipitating Silver
once a solution of NaCl is made up (because NaCl is cheep and easily dissolvable) it can be added little by little mixing throughout. No more silver is present once no cloudy precipitate is forming. The precipitate looks like the above picture.
Step 4: Filtration
The silver chloride that has resulted from the two solutions mixing can now be filter with a small round filter cut from a coffee filter and a vacuum flask shown. Remember to also weigh and write down how much the filter weighs.
Step 5: Drying
The filter paper can be dried on a watch glass in a 100 degree Celsius oven for a few hours. A typical chemical oven is shown.
Step 6: Weighing and Analysis
The filter paper is now dry and ready to be weighed. The previously recorded filter paper weight can be subtracted from the filter paper plus AgCl weight. This number can then be multiplied by the molecular ratio of silver to chloride in the molecule to get the weight of silver! You can also use this number to calculate how much you recovered compared to what was expected with chemical calculations. Solid silver chloride is shown above.