Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.
The beautiful colors in some forms of pottery can be formed by applying silver carbonate prior to heating the pottery. Under the heat of burning, the pottery the silver carbonate turns into beautiful colors.
Silver carbonate has the formula of Ag2 CO3. CO3 has a -2 charge, and each silver (Ag) atom has a +1 charge. So, the carbon is bound to three oxygen atoms. One carbon-oxygen bond is a double bond, while the other two are single bonds, putting the negative charges on two of the oxygen atoms. The silver atoms connect to the oxygen atoms with an ionic bond.
Silver carbonate has a molecular weight of 275.7 g/mol. It has a melting point of 424 degrees Fahrenheit (218 degrees Celsius), which means it is typically found as a solid. But it decomposes, or the bonds break apart, at 248 degrees Fahrenheit (120 degrees Celsius), so long before it gets to the melting point. It forms light-yellow crystals.
With the ionic nature of the bonds you would expect silver carbonate to be highly soluble in water. Typical these types of ionic bonds will ionize in water, allowing it to dissolve into the water (attracted to the partial positive and negative charges on water). But the ionic bond between the silver and carbonate is very strong, meaning that it doesn't readily ionize. Due to the lack of ionization, silver carbonate has very little solubility in water. At room temperature the solubility in water is 0.032 g/L.
As the temperature increases, the solubility of silver carbonate greatly increases. Recall that the decomposition temperature of silver carbonate is 120o C, this means that the bonds are all broken down at 120 degrees. Since the ionic bonds are the weakest bonds (weaker than the covalent bonds between carbon and oxygen) in the molecule, these will break down first as the temperature approaches 120.
So, when water is boiling, at 100o C, the temperature is pretty close to the temperature of decomposition, and the solubility of silver carbonate has increased to 0.5 g/L. This is still quite a bit lower than other ionic compounds, such as salt (which has a solubility of 359 g/L). So, we can't blame the entire lack of solubility on its inability to ionize, so what else is going on?
Despite the charge on silver it does not dissolve well into water. The size of the silver molecule makes it difficult for it to dissolve into water, so instead it precipitates out.
Silver Carbonate, Ag2 CO3. It is a solid, with light-yellow crystals, at room temperature, and decomposes at 120 degrees Celsius.
Despite the positive charge on silver and negative charges on the carbonate silver carbonate has a very low solubility. The ionic bond is fairly strong, but it is completely decomposed at 120 degrees, so the solubility does increase as the temperature of the water increases. But even at boiling temperatures the solubility is still fairly low, at 0.5 g/L. This is due to the size of the silver molecule, the water cannot hold it in solution and thus is precipitates out.
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