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This is an experiment to determine relative rates of hydrolysis of the halogenoalkanes.

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Introduction

AS - ASSESSED PRACTICAL HYDROLYSIS OF HALOGENOALKANES Introduction This is an experiment to determine relative rates of hydrolysis of the halogenoalkanes. The carbon - halogen bond is polarised: C X . The positive charge, + , on the carbon promotes nucleophilic attack which can results in the displacement of the halide: X (aq) ion. Halogenoalkanes, such as C4H9X + OH C4H9OH + X Each halogenoalkane has a different bond strength, bond polarity and varying electronegativities: C Cl C Br CI I Halogenoalkane Electronegativity Bond Length Bond Enthalpy C Cl Cl = 3.0 0.177nm 338 kJ mol C Br Br = 2.8 0.193nm 276 kJ mol C I I = 2.5 0.214nm 238 kJ mol As you can see from the table, the halogens decrease in electronegativity from Chlorine to Iodine, this forms a less polar molecule and therefore a smaller + charge on Carbon. However, the Carbon-Halogen bond length increases from Chlorine to Iodine and the bond becomes weaker and is consequently more easily broken. ...read more.

Middle

+ (9 x 1) +35.5 =92.5gmol-1 Density = 0.890gm -2 Volume = mass Volume of one mole = 92.5 0.890 = 10.4cm 3 Volume of 0.05 moles = 4.625 0.890 = 5.2cm3 Volume of 0.025 moles = 2.3125 0.890 = 2.6cm3 I think it would be best to use 0.025 moles of each halogenoalkane 1 - Bromobutane Molar mass of CH3CH2CH2CH2Br = (4 x 12) + (9 x 1) + 80 = 137gmol-1 Density = 1.28gcm-2 2.5% of 137gmol-1 = 3.425gmol -1 Volume of 0.025moles = 3.425 1.28 = 2.7cm3 1 - Iodobutane Molar mass of CH3CH2CH2CH2I = (4 x 12) + (9 x 1) + 127 = 184gmol-1 Density = 1.62gcm-2 2.5% of 184gmol-1 = 4.6gmol -1 Volume of 0.025moles = 4.6 1.62 = 2.8cm3 Method 1. Measure out 2cm� of Ethanol and put into a test tube. Repeat this twice more so that you have three test tubes each with 2cm� of ethanol in each. ...read more.

Conclusion

of silver nitrate solution * The temperature of the water bath Safety/Environmental care * Take care when using the hot water * The aqueous residues will contain the heavy metal ions on Ag and the organic residues will contain halogenated hydrocarbons so it is important not to dispose of any waste down the sink. Fair Testing * Use same volume for each solution * Make sure you use different teat pipettes for each halogenoalkane else they will get contaminated and the experiment will not be a fair test. Prediction Looking back on the scientific research that I have carried out, I think that the 1 - iodobutane will react fastest due to the weaker bond enthalpy and the longer bond length. This will overcome the fact that the Chlorine has a higher electronegativity than any of the other halogens and will therefore be the slowest to react. Sources Used * Text books: Chemistry 1, Chemistry for you, Laboratory guide, Chains and Rings * www.sciencenet.org.uk Kimberley Davies 7410 AS Chemistry Practical Assessment 53621 ...read more.

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