1/05/2013 Week 3 Wednesday Home

A similar experiment was was undergone by Dmitri Mendeleev (Analytical and Bioanalytical Chemistry, 2009, V 395 (1) 2009, p7-8)) where ratios of volume contraction through water and alcohol were tested and he felt that a ratio of 1:3 ethanol to water resulted in the best contraction. A report of some of his work can be found here.

http://seniorchem.com/mendeleyev_vodka.pdf

With this information in mind the first part of my EEI will conduct an experiment to test the validity of this statement by Mendeleev. Earlier on I talked about a possible hypothesis where I stated the higher the water ratio is to alcohol, the larger the resulting contraction will be, this hypothesis alone will not be the sole research question into my EEI, however I will have several hypotheses/research questions that I will investigate.

The first section of my EEI will test Mendeleev's research by testing the following ratios, 1:2, 1:3 and 1:4 (I will not be testing 1:1 as I feel the contraction will be minimal when compared to other ratios). I will be doing 3 repeats of each individual test resulting in 9 overall tests to have a wide spread of data and ensure accuracy. This first section of my EEI will be a relatively short one as this initial experiment will not take long.

I decided upon the separate alcohol and water mixture to equal 100mL. Mendeleev during his experiment found this perfect ration only through the volume contraction of ethanol as pure ethanol is pure alcohol and  very common. I will be taking this one step further and testing the following alkanols; methanol, ethanol and propanol resulting in a total of 27 tests including repeats once all alcohols are tested. From this information I will be able to analyse how the volume contraction affects different alcohols at different rations and determine whether the ratio of 1:3 is optimal for all three alcohols or whether their chemical structure and hydrogen bonding effects the overall volume contraction. 

I hypothesise that the optimal ratio for volume contraction will 1:3 for all alkanols and that as the molecular complexity of each alkanol increases the volume contraction will be larger.

I hypothesise this as volume contraction is a direct result of hydrogen bonding from the Oxygen  molecule bonding to the Hydrogen's  connected to the carbon chains of the alkanols, when these hydrogen bonds occur they ultimately surround and compress the alkanol molecule. As alkanol carbon chains get larger e.g. methanol, ethanol, propanol etc.. there are more readily available hydrogen's available to bond, therefore a more complex alkanol should result in a large volume contraction.

If all is said and done I will further test the validity of the volume contraction by testing how well it performs under temperature changes. I have researched how hydrogen bonds are effect by temperature and an increase in temperature results in molecules moving fast therefore effecting the hydrogen bonds. 

I hypothesise that an increase in temperature will result in a reduction in volume contraction.

I hypothesise this because the increased temperature should have faster moving molecules which should result in weaker hydrogen bonds. Weaker hydrogen bonds suggest that a smaller contraction will occur as they will not compress the alkanol as much.

Overall these tests should provide a lot of depth hydrogen bonding and inter molecular forces.