Making careful lab measurements is an essential skill for all chemists. This lab practical is designed to be a refresher on basic lab skills and then test your abilities to make specific solutions. Your task is to prepare about 50 ml of a Ca(II) solution with 500 ppb Ca(II) by weight with an accuracy of better than 1%. Your grade will be based entirely on your ability to meet this concentration target.
Below are references to specific lab apparatus and some helpful hints. Use these resources to prepare your test solution. Every aspect of this lab must be your own work. You may not share calculations, solutions, or procedures with other students. Your lab notebook must contain all of the details specific to your solution preparation. Do these calculations before coming to lab.
Available reagents: Solid CaCO3, CaCl2, distilled water, dilute acids and bases.
Equipment and Instructions:
- Mass Measurement: Harris, section 2-3 and Mettler Manual
- Burets, Volumetric Flasks, and Pipettes: Harris, sections 2-4 to 2-6
- Drying and Calibration: Harris, sections 2-8 and 2-9.
Hints: Please consider the nature of the reagents. Is the reagent a primary standard? Is the reagent dry? Is it soluble? How much sample do you need? What are the practical limits of the equipment available to you. We don’t need to make 500 liters of the Ca standard, but you also should plan on working with reasonable quantities of all reagents.
Evaluation: Fill an ICP tube with your test solution and bring it to the instrument lab for analysis by ICP. We will analyze your samples while you wait. You will receive full marks if you sample is 500 ppb in Ca(II) (within the analytical uncertainty of the instrument). If your sample fails the test you must remake the sample until you prepare the solution correctly. You will receive a 20% penalty for each try, so it is to your advantage to plan you work carefully.