way of determining the concentration of an unknown When bases like sodium hydroxide or calcium hydroxide sit around exposed to air, they can be neutralized by carbonic acid that forms from carbon dioxide and water that combine in the air. This happens at a relatively slow rate. Still, the potency of the base can decrease significantly over time. It is always a good idea to standardize old reagents before you use them to do quantitative work The Scenario Professor Ndekele asks you to check the status of reagents in an old cabinet in the lab. You find a jar labeled Ca(OH)2 which contains disc-shaped white crystals. You decide to perform a titration to verify its purity. Observations You make the following essential observations: 1. You dissolve 5.00 g of the crystals from the Ca(OH)2 jar in enough water to make 100.0 mL of solution. You find that there is a small amount of white solid that won't dissolve, so you separate it off by filtration. 2. You titrate three 10 mL aliquots of your solution with 1.00 M HCl(aq) and obtain the following data Trial V Ca(OH)2 (mL). V HCl (mL) 1 10.1 12.8 2 10.3 13.0 3 10.0 12.7 Analysis 1. Determine the expected concentration of the solution you made by dissolving 5.00 g of solid calcium hydroxide in enough water to make 100.0 mL of solution (this is assuming the the calcium hydroxide is not at all degraded) 2. Determine the concentration of calcium hydroxide solution for each trial in the titration, and also determine the average value for the three trials