Cracking Chemical Equation

[Salomon Thoj]

Whattype of reaction is cracking?","acceptedAnswer":"@type":"Answer","text":"Cracking is the process of breaking down-longer chain hydrocarbon fractions from the fractional distillation of crude oil into shorter-chain hydrocarbons. It is a type of thermal decomposition reaction."},"@type":"Question","name":"What is cracking used for in chemistry?","acceptedAnswer":"@type":"Answer","text":"Cracking is used to break longer-chain hydrocarbons into shorter-chain hydrocarbons, including alkenes. Longer-chain hydrocarbons aren't very useful and have a low demand, whilst short-chain hydrocarbons have multiple uses and a high demand. As a result, cracking increases the economic value of longer-chain hydrocarbon fractions.","@type":"Question","name":"How is cracking carried out?","acceptedAnswer":"@type":"Answer","text":"Thermal cracking involves heating the longer-chain hydrocarbons to a very high temperature (700 - 1200 K), under high pressure (7000 kpa). Catalytic cracking involves heating the longer-chain hydrocarbons with a zeolite crystal catalyst to a high temperature (700 K), under a slightly raised pressure.","@type":"Question","name":"What conditions are needed for cracking?","acceptedAnswer":"@type":"Answer","text":"Thermal cracking requires a temperature of 700-1200K and a pressure of 7000 kPa. Catalytic cracking requires a zeolite catalyst, a temperature of 700K, and a slightly raised pressure.","@type":"Question","name":"What are the products of cracking?","acceptedAnswer":"@type":"Answer","text":"Cracking produces shorter-chain alkanes and alkenes."]} #ab-fullscreen-popup display: none; Find study contentLearning Materials

But cracking doesn't have to be a bad thing. Sure, smashing a plate isn't much fun, but unless you break open an egg, you'll never be able to make an omelette with the tasty white and yolk inside. Cracking an object into smaller pieces to make it more useful is much like chemical cracking.

When we crack a Christmas cracker, we snap it in half to reveal a silly joke and paper hat. When we crack a coconut, we are rewarded with a feast of refreshingly cool coconut water. In both cases, we break a larger object apart into smaller pieces to make it more useful. This also happens in cracking in chemistry.

The term cracking is most commonly used to describe the breakdown of long-chain hydrocarbon fractions from crude oil into shorter-chain alkanes and alkenes. This involves breaking a C-C single bond. The cracking of hydrocarbons will be the main focus of our article today.

The usefulness of different crude oil fractions creates a problem: Their supply doesn't meet their demand! For example, crude oil from the North Sea typically contains over 88% long-chain C10+ hydrocarbons1. We end up with a lot of spare longer-chain hydrocarbons and not much to do with them!

However, there is a solution. To make surplus longer-chain fractions more economically valuable, we can crack them into more useful products. The hydrocarbons produced have a much higher demand and are a lot more useful to us than the original longer-chain hydrocarbons, making cracking an economically significant reaction. Let's explore the products of cracking now.

The process is random, meaning that we can't control exactly which molecules we end up with. However, it doesn't matter so much - both types of products are much more useful to us than the original longer-chain hydrocarbons. With cracking, we can turn relatively useless molecules that we probably wouldn't otherwise use into relatively useful molecules that massively enhance our lives.

Cracking firstly produces short-chain alkanes. These, as we already know, have a higher demand than longer-chain hydrocarbons. They're used primarily as fuels, but also in cigarette lighters, aerosols, and more.

Because hydrocarbons like alkanes are relatively unreactive due to their strong, non-polar C-C and C-H bonds, both types of cracking require particularly harsh conditions to break them down. However, they also have their differences. Let's look at types of cracking now.

Thermal cracking involves putting the hydrocarbon alkanes under extreme heat and pressure for a brief period of time, usually only one second. We typically use a very high temperature of 700-1200 K and a high pressure of 7000 kPa. The alkane splits homolytically, meaning one electron from the bonded pair goes to each of the new molecules formed. This forms two free radicals.

Free radicals react further to produce various hydrocarbons, but especially alkenes. However, maintaining such extreme conditions requires a lot of fuel. Therefore, thermal cracking has a large economic and environmental footprint.

Catalytic cracking produces a high proportion of shorter-chain, branched, and cyclic alkanes, as well as aromatic compounds such as benzene. It also has much lower fuel requirements than thermal cracking.

Cracking is a largely random process. It is impossible to predict exactly which molecules will be produced. This means there are multiple different equations and potential products for each reaction, and your examiner could test you in various ways. This will typically involve finding an unknown hydrocarbon reactant or product. However, it's easy enough to 'crack' cracking equations! The important thing to remember is that the equation has to be balanced: the numbers of carbon atoms and hydrogen atoms on each side of the equation must be the same.

We can carry out the same process with hydrogen. This will give us a value for y. There are twenty-two hydrogen atoms on the left-hand side, and so we need twenty-two on the right. We already have eighteen hydrogen atoms in the first product, octane, and so there are \(22-18=4\) hydrogens remaining. Therefore, \(y=4\).

Now we can balance the equation. The only reactant on the left-hand side of the equation is X, our unknown, and so we know that x and y must equal the total number of carbon atoms on the right-hand side. Likewise, y must equal the total number of hydrogen atoms on the right-hand side.

Cracking is the process of breaking down-longer chain hydrocarbon fractions from the fractional distillation of crude oil into shorter-chain hydrocarbons. It is a type of thermal decomposition reaction.

Cracking is used to break longer-chain hydrocarbons into shorter-chain hydrocarbons, including alkenes. Longer-chain hydrocarbons aren't very useful and have a low demand, whilst short-chain hydrocarbons have multiple uses and a high demand. As a result, cracking increases the economic value of longer-chain hydrocarbon fractions.

Thermal cracking involves heating the longer-chain hydrocarbons to a very high temperature (700 - 1200 K), under high pressure (7000 kpa). Catalytic cracking involves heating the longer-chain hydrocarbons with a zeolite crystal catalyst to a high temperature (700 K), under a slightly raised pressure.

CrackingclosecrackingThe breaking down of large hydrocarbon molecules into smaller, more useful hydrocarbon molecules by vaporising them and passing them over a hot catalyst. is a reaction in which larger saturated hydrocarbonclosehydrocarbonA compound that contains hydrogen and carbon only. moleculesclosemoleculeA collection of two or more atoms held together by chemical bonds. are broken down into smaller, more useful hydrocarbon molecules, some of which are unsaturated:

The starting compound will always fit the rule for an alkane, CnH2n+2. The first productcloseproductA substance formed in a chemical reaction. will also follow this rule. The second product will contain all the other C and H atoms. The second product is an alkene, so it will follow the rule CnH2n.

C16H34 is an alkane which can be used as the starting chemical in cracking. One of the products of cracking this compoundclosecompoundA substance formed by the chemical union of two or more elements. is an alkane which has 10 carbon atoms in it. Write a balanced symbol equation for this cracking reaction.

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 distillationclosefractional distillationIn fractional distillation a mixture of several substances, such as crude oil, is distilled and the evaporated components are collected as they condense at different temperatures. of crude oilclosecrude oilMixture of hydrocarbons, mainly alkanes, formed over millions of years from the remains of ancient dead marine organisms. produces more of the larger hydrocarbons than can be sold, and less of the smaller hydrocarbons than customers want.

Smaller hydrocarbons are more useful as fuelsclosefuelMaterial that is used to produce heat, like coal, oil or gas. than larger hydrocarbons. Since cracking converts larger hydrocarbons into smaller hydrocarbons, the supply of fuels is improved. This helps to match supply with demand.

As a result, alkenes are more reactiveclosereactiveThe tendency of a substance to undergo a chemical reaction. than alkanes. Alkenes can take part in reactions that alkanes cannot. For example, ethene molecules can react together to form poly(ethene), a polymerclosepolymerA large molecule formed from many identical smaller molecules known as monomers..

More loosely, outside the field of petroleum chemistry, the term "cracking" is used to describe any type of splitting of molecules under the influence of heat, catalysts and solvents, such as in processes of destructive distillation or pyrolysis.

At that time, just a few years after the Russian Revolution and brutal Russian Civil War, the Soviet Union was desperate to develop industry and earn foreign exchange, so their oil industry eventually did obtain much of their technology from foreign companies, largely American.[4] At about that time, fluid catalytic cracking was being explored and developed and soon replaced most of the purely thermal cracking processes in the fossil-fuel processing industry. The replacement was not complete; many types of cracking, including pure thermal cracking, still are in use, depending on the nature of the feedstock and the products required to satisfy market demands. Thermal cracking remains important, for example, in producing naphtha, gas oil, and coke, and more sophisticated forms of thermal cracking have been developed for various purposes. These include visbreaking, steam cracking, and coking.[5]

3a8082e126