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Introduction

Chemistry Lab Report - Investigating the properties of period 3 Chlorides Introduction: Aim: To study the chlorides of period 3 elements and classify them according to structural type and bonding. Hypothesis: If the compound dissolves in the water there may be a temperature change. If it's a small temperature change, then this will indicate that a physical process has taken place. While a large temperature change will indicate that a chemical process has taken place. This will help distinguish between the physical process of dissolving and chemical one of hydrolysis when you add these substances to water. And if there are any pH changes that take place when the chlorides are reacted with water. A decrease in pH will indicate that hydrolysis has taken place. Finally, consider a physical data for each compound and reach a conclusion its bonding and structure. General Background: As the number of valence electrons increases, there is a steady increase in the number of electrons available for bond formation and hence in the number of chlorine atoms that each element bonds to - NaCl, MgCl2, AlCl3 (more correctly written as Al2Cl6 in its gaseous state), SiCl4, PCl5 (though PCl3 also exists). The chlorides of metals, such as sodium chloride and magnesium chloride, are ionically bonded crystalline solids with high melting points. When added to water these chlorides dissolve without chemical reaction, to give solutions in which the component ions can behave independently. ...read more.

Middle

has any gas evolved at any time? If so, is the gas acidic? Can it be identified using a simple test? 5) Using either universal indicator solution (2 - 4 drops) or a piece of pH paper, I compared the colour with the chart provided, and noted the pH indicated. 6) All the above steps were repeated for the rest of the chloride samples (MgCl2 and AlCl3) provided. 7) For comparison with the above, measure the pH of the distilled water in a test tube by using either universal indicator or pH paper. 8) On mixing with acetone, repeat the steps of that of water, only now using acetone. This time, there is no need to examine the pH. Results: Data collection: a) On mixing the given chlorides with water: Note: pH of water = 7 Appearance NaCl MgCl2 AlCl3 Initial temperature 29�C 29�C 29�C Final temperature 29�C 31�C 77�C Does it dissolve Yes Yes Yes pH of solution 8 9 10 Other observations (if any) - Gas released (pH 5), solution turned green Heat was released, effervescence occurred, gas released had a pH of 5 b) On mixing the given chlorides with cyclohexane (acetone): Appearance NaCl MgCl2 AlCl3 Initial temperature 28�C 28�C 28�C Final temperature 29.5�C 29�C 56�C Does it dissolve No Yes Yes Other observations (if any) - - Solution began bubbling, heat was released c) ...read more.

Conclusion

Evaluation: During the experiment there were a couple of errors in the measurement of the temperatures and pH of the solutions, and in the volume of distilled water used. Weaknesses in my method (Sources of error): * While measuring the pH of the solutions it was a bit hard determining the colour change to compare with the pH colour chart. * A measuring cylinder was used to measure the volume of distilled water used. * When the thermometer was placed in the solution of aluminium chloride and water/ acetone, the temperature increased rapidly and so it was hard to follow the meniscus of mercury and note the highest reading. Prevention of those errors: * When measuring the pH of the solutions, a white tile or even white piece of paper should be kept behind the test tube so as to find out the correct colour change to be compared with that on the pH colour chart. Usage of a digital pH meter would make the results much more accurate. * A pipette should be used instead of a measuring cylinder in order to accurately measure the volume of the distilled water. * The error due to the thermometer could be improved by repeating the measuring of the temperature of aluminium chloride with water/acetone at least five times, and finding the average value. Otherwise, a digital thermometer could be used to improve the accuracy of the results. ?? ?? ?? ?? Teacher: Minati Sahu Chemistry Lab Report - Period 3 Chlorides Kelwin Joanes Page 1 of 8 ...read more.

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