Planning to crack alkanes experiment

This microscale experiment offers a potential solution. It uses a far smaller quantity of chemicals than the traditional set-up reducing the amount of fumes produced and does not have the problem of suck-back of cold water into a hot tube.

This experiment is far quicker than the traditional version. How long it takes a class depends on how familiar students are with the microscale equipment, but should easily be completed in 30 minutes. You also need to leave enough time for the equipment to cool before it is dismantled. The equipment can be set up for the students if they are likely to find putting all the pieces together very difficult. It may be that you do not wish to buy the microscale equipment for just this one experiment.

The main hazards are ethanol, the glass tubing and bromine water. Due to the nature of the hazards, eye protection should be worn at all times during this experiment, including set up and dismantling. Students should be warned about the dangers of the ethanol in the microburners. They should keep the burner upright and should not take off the lid. Ethanol produces highly flammable vapour and can catch fire very easily.

To minimise any risk, ensure that the burners are filled prior to the lesson. Students need to light their burners, and the easiest way to do this is with matches - take a flame to the burner, not the burner to a flame.

It is probably advisable to have a box of matches per bench, to know how many boxes you have and to count them out at the start and in at the end of the session. Having a limited number of matches in each box reduces the potential for mischief. As an alternative, have a lit Bunsen or two in the laboratory and have students use splints to light their burners. However, they can be tricky to light this way. The students should take care when handling glass tubes to ensure that they do not break and cut their hands.

The tube should be held near the end that the tubing is being attached to to allow minimal flexion and a lower likelihood of cuts. The tubing could be pre-attached for students.

Apart from these hazards, the main management issue in this practical is likely to be how well students cope with being asked to set up perhaps unfamiliar equipment.

It is worth checking that their equipment is set up correctly and that they understand how to use it before they begin heating. How to set up the equipment for cracking hydrocarbons in liquid paraffin on a microscale.

The hole and therefore the drop size of a pipette can vary. Therefore it is a good idea to try out this practical before the students do it. This is to ensure that sufficient alkene is being generated to discolour the bromine water.

The word paraffin comes from Latin and means little or small affinity and this connects to alcanes, because they do not combine or react with other substances in normal conditions usually.

Because we did not have bromine water in our lab, we did not conduct the experiment that would answer this question. In which substance is potassium manganate VII more soluble — hexane or water? It is more soluble in water, because they are both polar substances. Data presentation: Pictures III. Chemical properties: Action of common reagents on hexane None of the reagents used reacted with hexane and thus as in the first experiment the two substances were separated. Evaluating procedure: One of the possible errors in this experiment would be human error, seen when we needed to take exact volumes of the reagents.

Improving investigation: This experiment could be improved by test-re-test method, but because we had limited time that was not an option for us, so altogether more time would be needed, to eliminate random errors. Share this: Twitter Facebook. Like this: Meeldib Laen Seotud postitused. Option C. Practical Carbonyl compounds. IB Chemistry blog. Sign me up.

Already have a WordPress. Related Audiobooks Free with a 30 day trial from Scribd. Outstanding Leadership Stan Toler. So you do not need to waste the time on rewritings. Nur Anis Atiqah Idrus. Show More. Views Total views. Actions Shares. No notes for slide. Planning and Designing Lab 1.

Aim The purpose of carrying out this experiment is to identify Alkanes and Alkenes by their reactions with different substances and determine their properties. Introduction In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls. Aromatic hydrocarbons arenes , alkanes, alkenes, alcohol, esters and alkyne-based compounds are different types of hydrocarbons.

The majority of hydrocarbons are found naturally occurring in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate to form seemingly limitless chains.

Hydrocarbons are divided into two classes known as aliphatic compounds and aromatic compounds. Aliphatic compounds are namely alkanes and alkenes.

In this experiment, the hydrocarbons that are being used to identify and determine their properties are cycloalkane and cycloalkene which are from group alkane and alkene respectively.

Alkanes are the simplest family of hydrocarbons compounds that contain carbon- hydrogen bonds and carbon-carbon single bonds. The carbon-hydrogen bonds are only very slightly polar and so there are no parts of the molecules which carry any significant amount of positive or negative charge which other things might be attracted to.

The net effect is that alkanes have a fairly restricted set of reactions. Thus, alkanes can only undergo combustion, 2. Alkanes are not very reactive and have little biological activity.

An isomer, in part, similar to a chemical anagram but unlike an anagram, may contain varying number of atoms and components, for which in a chemical compound can be structurally arranged in a multitude of different combinations and permutations. The simplest isomer of an alkane is the carbon atoms are arranged in a single chain with no branches.

However the chain of carbon atoms may also be branched at one or more points. The number of possible isomers increases rapidly with the number of carbon atoms. Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond. Alkenes are relatively stable compounds but are more reactive than alkanes due to the presence of a carbon- carbon double bond.

The majority of the reactions of alkenes involve the rupture of this carbon- carbon double bond, forming new single bonds. Thus, the main reaction of alkene is addition such as hydrogenation, halogenation and oxidation. The formula of alkene is CnH2n where n starts from 2,3,4,5 and so on. Thus, the first member of alkene family is ethene with a formula of C2H4.

The angle may vary because of steric strain introduced by non-bonded interactions created by functional groups attached to the carbons of the double bond. The test tube is shaken well and is observed after two to three minutes. A second test tube is prepared similarly. The first test tube is placed in a laboratory locker and the second is placed in bright sunlight. Both of the test tubes are allowed to stand for minutes and both were then compared.

The color of the solution in each test tube is observed. The results are recorded. Steps are repeated with alkene, with just one test tube of sample. There is no need for sunlight reaction. The tube is shaken for minutes and the results are noted. Steps are repeated with alkene and the results are noted. Sulphuric Acid Test 1. The hexane is passed over a hot catalyst.

Butane and ethene are produced. Cracking is important for two main reasons:. The supply is how much of a fraction an oil refinery produces. The demand is how much of a fraction customers want to buy. Very often, fractional distillation of crude oil produces more of the larger hydrocarbons than can be sold, and less of the smaller hydrocarbons than customers want.