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An investigation to compare and determine the concentrations of some alkalis in saturated solution.

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Introduction

An investigation to compare and determine the concentrations of some alkalis in saturated solution. Introduction Hydroxides from group 1 of the periodic table are stronger alkalis than those from group 2. Reason being that group 2 hydroxides have lower solubilities. Group1 hydroxides are soluble in water. When these hydroxides undergo titration with acid, the end products are usually salt and water. For example, NaOH (aq) + HCl(aq) H2O + NaCl(aq) An acid based titration is a procedure used to determine concentrations. It involves the neutralization of the base with an acid, both in aqueous solution. It indicates an equivalence point (this can also be termed 'end-point'). This is the point where the colour of the base permanently changes to a pink colour, representing its neutralization. The point is clear to us with the use of an indicator. In this case, the indicator phenolphthalein will be used as Ethanedioic acid is being used. This indicator is chosen because the titration is of a weak acid and a strong base. Metal hydroxides that are soluble make strong bases. It is necessary to construct primary standard solutions when finding out concentrations of solutions. They need to be of a known concentration. ...read more.

Middle

This is the point where the base is neutralized. Following this, a set of three or four accurate titres should be carried out. To ensure accuracy of the end-point and to make sure that it is not missed, it is important to add the acid from the burette in drops. 1. Pour the primary standard solution prepared earlier into the volumetric flask using the funnel to avoid spillage. 2. Add more distilled water to the solution in the volumetric flask to make the total volume 250cm3 3. Put the stopper of the flask on it and shake vigorously a good few times to make sure that all the contents are dissolved thoroughly. 4. Label this solution 5. Using the pipette filler, fill the glass pipette with Sodium hydroxide solution from the volumetric flask 6. Release the contents of the pipette into a conical flask and add 4 drops of phenolphthalein indicator 7. Fill the burette fully with Ethanedioic acid, making sure that the tap is closed to prevent the leakage of the acid, and with the miniscus at eye level reading 0 8. Record this initial reading 9. Record all data to two decimal places. 10. Open the tap of the burette and titrate the acid with the solution. ...read more.

Conclusion

* Long hair must be tied back * Bottles must be kept away from the edge of the bench to avoid spillage * Certain apparatus should be handled with extra care, such as glassware. This applies especially when they are filled with contents * Make sure that the tap of the burette is properly closed when filling it, to avoid leakage of the acid. * Fill the burette using a funnel to avoid spillage * All spillages should be mopped and cleaned up immediately to prevent damage and injury to others Reliability and Precision * To ensure accurate quantities of acid and hydroxide solutions, a Gilson pipette could be used * The inside of the burette must be thoroughly rinsed to avoid dilution or increased concentration of the acid. * The pipette should also be rinsed * Ensure that all the contents from the pipette is emptied into the conical flask. If not, this could lead to inaccurate volume being used * When reading off the burette, make sure you are at eye level with the miniscus * When recording the readings, record to two decimal places * The end-point can also be determined using a colorimeter, just to ensure further accuracy * It is recommended to repeat each experiment at least 3 to four times ?? ?? ?? ?? Chemistry Practical Assessment: Planning Jaspal Kaur Attalia ...read more.

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