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2-13:CreatingaSolutionofKnownMolarity

In this assignment, you will weigh out asample of baking soda (NaHCO3) and create a solution ofknown molarity.

1.    Start VirtualChemLab, select Reactions and Stoichiometry,and then select Creating aSolution of Known Molarityfromthe list of assignments.The lab will open in the Titration laboratory.

2.    In the laboratory, a bottle of baking soda (sodiumbicarbonate, NaHCO3) will be next to thebalance, and an emptybeaker will be on the stir plate.  Drag the emptybeaker to the spotlight next tothe balance, clickin the Balance area to zoomin, place aweigh paper on the balance, and tare the

balance.

3.    Open the bottle by clicking on the lid (Remove Lid). Pick up the Scoopand scoop out some sample by first dragging the scoop tothe mouth of the bottle and then pullingthe scoop down the face of the

bottle. As the scoop is dragged down the face of the bottle it will pickup different quantities ofsolid. Select the largest sample possible and drag the scoop tothe weighing paper on the balance until it

snaps in place and then let go.  This will put approximately1 gofsample on the balance.  Repeat

with a second Scoop. Record the mass of the NaHCO3  in the data table.

4.    Drag the weigh paper to the beaker and add the NaHCO3  sample tothe beaker. Click on thegreen

Zoom Out arrow to return tothe laboratory.

5.    Drag the beaker to the 50mL graduated cylinder (thelargest one) by the sink and emptythe sample

into the cylinder.  Hold thecylinder under the tap until it fills withwater tomake an aqueous solution

of NaHCO3. (When the graduated cylinder is full it will automatically snap back into place.) Note that the solid is added and dissolved before the volume ismeasured whenmaking a molar solution.

Chemists normallyuse a volumetric flask for making molar solutions, but this is not available in the simulation.

6.    Determine the liters of solution inthe cylinder and record the data in thedata table.

7.    Determine the moles of NaHCO3  in the sample and record the datain the data table.

DataTable

8.    Themolarityis calculated using the formula:

mass solute

molarity =                    =                    molarmasssolute

Lsolution

Lsolution

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Virtual ChemLab: General Chemistry, Student Lab Manual/Workbook, v4.5, Third Edition, by Brian F. Woodfield and Matthew C. Asplund. Published by Prentice Hall.

Copyright © 2013 by Pearson Education, Inc.