the nearest 0.01g.
2. Put the solute into the beaker, and wash down the rest with the wash bottle.
3. Stir to dissolve the solid, adding more water if necessary.
4. Transfer the solution to the volumetric flask through the filter funnel. Rinse the
beaker well, making sure all liquid goes into the volumetric flask.
5. Add distilled water until the level is within about 1 cm of the mark on the neck of
the flask. Insert the stopper and shake to mix the contents.
6. Using the dropper, add enough water to bring the bottom of the meniscus to the
mark. Insert the stopper and shake thoroughly ten times to ensure complete
mixing.
Results and Calculations
Discussions
1. What effect would each of the errors described below have on the concentration
of sodium carbonate?
- Some of the solid sodium carbonate was spilled in making the transfer.
The concentration of sodium carbonate will record a lower value than its true value because by n=m/M , since mass decrease, the number of mols of Na2CO3 will decrease. Then Concentration of the Na2CO3 is calculated by (no of mol of Na2CO3/Volume of solution) so that when no of mol of Na2CO3 decrease , the concentration will decrease.
b) Not enough water was added to bring the volume up to the mark.
The concentration of sodium carbonate will record a higher value than its true value because concentration of the Na2CO3 is calculated by (no of mol of Na2CO3/Volume of solution) so that when the volume of solution decrease , the value of Na2CO3 will larger.
I think there is a little error when I was perfoming the experiment. First, I forgot to rinsed the volumetric flask before the experiment, so that Na2CO3 solution may contaminated with some other solution and this will afftected the result. Also, I cannot add the water to the volumetric flask until the gratuation mark accurately, and there are an error about 1-2 cm3 and it will affect the concentration of Na2CO3 solution.
After doing the experiment , I found that every step is very important in preparing standard solution. If we missed some of the steps , the concentration of the solution can be greatly affected. For example, while we are weighting the Na2CO3, the top of the balance my contain some Na2CO3 , to make sure the experimet is accurate , we have to clean the solid on the top of the balance first . Also , we need to use washing the bottle to wash the beaker 2-3 times to make sure all the Na2CO3 is transferred into the volumetric flask. Besides , when we are adding the water to the graduation mark , our eye level must be same as the graduation mark . Also , we need to make the Na2CO3 solution in volumetric flask upsaide down to make sure that it is evenly distributed.
Conclusion The molarity of the standard solution is 0.1mol/dm3 .
