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Concept Map the Calculations

The way back-titrations are taught is often confusing. Get them to concept map the calculation. So, instead of trying to do the calculation in their head, map it out starting from where they end up, and then relate each of those steps to where that number is coming from. Have them think about it like it’s a reaction. Because they know how to do the math, and they can understand how to do it for a reaction. An example is the dissolution of calcium carbonate and trying to get them to work out how much carbonate is in a limestone sample. We use diprotic acid, so it’s got stoichiometry involved as well, and they quite often slip up on the stoichiometry problem, even at second-year level. Use that initial map that they’ve created to do the calculations and also map the uncertainties, so they can calculate an uncertainty in a multi-step process. That simple act of getting it out of their head and onto a piece of paper in a visual way works really well. You can do that as part of the pre lab, so get the group together, and create the map before doing the actual experiment.

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