Precipitation of Silver Chromate
When clear, colorless silver nitrate solution is added to transparent, yellow sodium chloride solution, red silver chromate precipitates.
This demo is typically performed when solubility rules are being presented. Allow two minutes for this demo.
Almost all alkali metal compounds and nitrates are soluble, but most silver compounds are insoluble (except for acetates, perchlorates, chlorates, and nitrates). Therefore, when the soluble salts silver nitrate and sodium chromate are mixed, insoluble silver chromate forms and precipitates out. (Ksp = 1.12 x 10-12) 2AgNO3(aq) + Na2CrO4(aq) --> Ag2CrO4(s) + 2NaNO3(aq) or 2Ag+(aq) + 2CrO4-(aq) --> Ag2CrO4(s) Silver nitrate is used in photography, medicine, silver plating and refining, and in making mirrors and indelible ink.2
- about 500mL 0.1M sodium Chromate solution
- dropper bottle of 0.1M silver nitrate solution
- glass cylinder
- background box
Place the glass cylinder in front of the background box to provide better visibility. The yellow background works best for this demo. Fill the cylinder about halfway with sodium chromate solution. Add several droppers full of silver nitrate solution to the cylinder. Immediately a red/orange precipitate forms.
Silver nitrate is a strong oxidizer, but the solution is fairly dilute. Wear goggles. Avoid getting silver nitrate solution on your skin. If your skin comes into contact with silver nitrate solution, immediately wash thoroughly with soap and water. If you get silver nitrate solution in your eyes, flush with water for 15 minutes and seek medical help. (But don't worry too much, this solution is about 1.5% by weight and 1% solution is used to treat eye infections.) also sodium Chromate is a carcinogen if there is a spill remove contaminated clothing and clean effected area with soap and water.
