Erin'sChemBlog: Murder Investigation Lab

Today in class, my lab partner and I finished conducting the Murder Investigation Lab. On Monday we started by reading about the different suspects for the murder of Miss Scarlet and wrote up a procedure in order to determine who did it. We first did double replacement reactions of potassium iodide and silver nitrate with sodium chloride and sodium carbonate in order to make predictions for the products of mixing the different solutions. Through these double replacement reactions, we were able to predict that the murder weapon was most likely silver nitrate.
By mixing the unknown solution with sodium carbonate, we were able to determine that the murder weapon was in fact silver nitrate based on the reaction forming a solid. We then used the funnel to get the solid that was formed by itself onto the filter paper. After letting the filter paper dry over night, we were able to take the mass of the filter paper with the solid, silver carbonate, that formed. By subtracting the mass of the filter paper from this measurement we can convert the mass of the silver carbonate that formed into moles. We then divide the moles of silver carbonate by the amount of unknown solution used in order to determine the molarity. Doing this, we were able to determine that the murderer was Mr. Green who used silver nitrate as the weapon.