Consequently, the molarity is one-fifth of its original value. Another common dilution problem involves deciding how much of a highly concentrated solution is requires to make a desired quantity of solution of lesser concentration.
The highly concentrated solution is typically referred to as the stock solution. Nitric acid HNO 3 is a powerful and corrosive acid. When ordered from a chemical supply company, its molarity is 16 M. How much of the stock solution of nitric acid needs to be used to make 8. Step 1: List the known quantities and plan the problem. The unknown in the equation is , the volume of the concentrated stock solution.
Step 3: Think about your result. The dilution is by a factor of 32 to go from 16 M to 0. Image 1. Volumetric pipette. Image from the Teaching and Learning Centre. Figure 2. Image by rocksee. Despite the hurdles, students are still determined to be scientists as they adapt to redesigned learning. College Life. Know Your Techniques: Solutions. Deposit Photos. Know what your concentration means There are many ways to measure and report concentration.
Download table PDF. Either way, the calculation for the mass of MgCl 2 needed is the same:. Nail the measurements Knowing which equipment to use is one thing.
Balances top-loading and analytical Balances are sensitive to vibrations and air currents. Keep balances isolated from both and wait until the reading stabilizes before recording the mass.
Weighing papers and boats have mass, too. Remember to zero tare your weighing paper or boat on the balance before adding the substance you are weighing. They may even be too tiny to see. Use a little bit of solvent to wash them into your flask. Volumetric flasks Volume and temperature changes are common when materials dissolve. If necessary, let the mixture sit until the solution comes to room temperature. Once the initial dissolution is complete, add solvent until the bottom of the meniscus barely touches the volume mark.
Volumetric flasks are calibrated to this standard, so be as fussy as possible. When working with a solute that releases heat or gas during dissolution, you should also pause and pull out the stopper once or twice. Use flasks for preparing solutions only. They are not meant for transferring solutions. Just because you have Use pipets for those measurements. When reading the volume, make sure your eye is level with the meniscus.
Volumetric pipets Volumetric pipets are calibrated for using vertically and with the bottom of the meniscus just touching the volume mark. Keep them upright and make sure your eye is level with the volume mark. Keep the tip of the pipet submerged in the solution the whole time to keep liquids from being sucked up into the bulb.
Sucking solutions into the bulb distorts your measurement and ruins the bulb. Let the pipet drain into your flask. A tiny bit of solution will remain in the tip, but the pipet was calibrated with that in mind, so leave it alone. Common equipment.
Left to right Wash bottle, volumetric flask and graduated cylinder. Dilute silver nitrate must be used because concentrated can cause blindness in extreme cases. Concentrated solutions have a lot of solute usually close to the maximum that can dissolve near "saturated" whereas dilute solutions have relatively little. Evaporate some solvent or add more solute. Try to be more precise; explain what you mean by the type of a function.
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