🤓 Based on our data, we think this question is relevant for Professor Gorman's class at LONESTAR.
We are asked what happened when you take a metal spatula and scratch the side of the glass vessel that contains a cooled solution of Cr(NO3)3•9 H2O and crystals start to appear.
The solubility of Cr(NO3)3 •9 H2O in water is 208 g per 100 g of water at 15 oC. A solution of Cr(NO3)3 •9 H2O in water at 35 oC is formed by dissolving 313 g in 100 g water. When this solution is slowly cooled to 15 oC, no precipitate forms.
You take a metal spatula and scratch the side of the glass vessel that contains this cooled solution, and crystals start to appear. What has just happened?