Chemistry (9-1) - 0971 CIE

Alkenes

Gbogbo ọrọ náà

If alkanes are the calm members of the organic world, alkenes are the reactive ones. The single feature that makes the difference is a carbon-carbon double bond, and it turns these molecules into the raw material for plastics, ethanol and much of the chemical industry.

In this lesson you will learn that alkenes are unsaturated hydrocarbons with the general formula CnH2n, how their double bond drives addition reactions, and how bromine water provides a quick chemical test to tell an alkene from an alkane.

Ebumnobi

State that the bonding in alkenes includes a double carbon-carbon covalent bond and that alkenes are unsaturated hydrocarbons.
Describe the manufacture of alkenes and hydrogen by the cracking of larger alkane molecules using a high temperature and a catalyst.
Describe the reasons for the cracking of larger alkane molecules.
Describe the test to distinguish between saturated and unsaturated hydrocarbons by their reaction with aqueous bromine.
[Supplement] State that in an addition reaction only one product is formed.
[Supplement] Describe the properties of alkenes in terms of addition reactions with: (a) bromine or aqueous bromine (b) hydrogen in the presence of a nickel catalyst (c) steam in the presence of an acid catalyst and draw the structural or displayed formulae of the products.

Akọmọ Ojú-ẹkọ

Alkenes are the starting point for an enormous range of products, from polythene bags to ethanol. Their reactivity, all because of one double bond, is what makes them so useful, and it is also the basis of a simple laboratory test you are expected to know.

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Ayẹwo Ẹkọ

Ekele diri gi maka imecha ihe karịrị na Alkenes. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

Alkenes are unsaturated because they contain a: A. Single bond only B. Carbon-carbon double bond C. -OH group D. -COOH group Answer: B
The general formula of the alkenes is: A. CnH2n+2 B. CnH2n C. CnH2n+1OH D. CnH2n-2 Answer: B
When bromine water is shaken with an alkene, it: A. Stays orange B. Turns blue C. Is decolourised D. Turns red Answer: C
Adding steam to ethene, with a catalyst, produces: A. Ethane B. Ethanol C. Ethanoic acid D. Methane Answer: B
Reactions in which a molecule adds across a double bond are called: A. Substitution reactions B. Addition reactions C. Combustion reactions D. Neutralisation reactions Answer: B