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iGCSE Chemistry > Organic Chemistry > Flashcards

Organic Chemistry Flashcards

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1
Q

What is the empirical formula? How is it related to molecular formula?

A

-Simplest whole ratio of atoms of different elements in the compound
-The two are related by some numerical constant
-CH2 = C7H14 (x7)

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2
Q

What is crude oil?

A

A mixture of compounds; a fossil fuel consisting of the remains of ancient biomass. It is also finite

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3
Q

What is a hydrocarbon?

A

A compound made up exclusively of hydrogen and carbon atoms

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4
Q

What are alkenes?

A

Saturated hydrocarbons of a general formula CnH2n+2

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5
Q

What is a homologous series?

A

series of compounds with same general formular, same functional groups and similar chemical properties

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6
Q

Describe the combustion of hydrocarbons

A

-Exothermic reaction occurring when hydrocarbons are reacted with oxygen
-Complete combustion produces carbon dioxide and water (carbon and hydrogen atom are completely oxidised)
-Incomplete combustion produces carbon or carbon monoxide and water

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7
Q

Describe the physical properties of alkenes

A

-First few in series are gases, then change to liquids, then to solids
-In general, boiling points and viscosity increase as molecules get biggest; volatility and flammability decrease as molecules get bigger
-Poor reactivity

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8
Q

Explain how fractional distillation of crude oil takes place

A

-Crude oil is heated and vaporised
-Vapor rises up the fractionating column
-The column is hotter at the bottom and cooler at the top
-Hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points.
-Large molecules, high boiling points-collected at the bottom
-Small molecules, low boiling points-collected at the top
-This gives fractions, which can be used in various ways

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9
Q

What is cracking?

A

WHen large hydrocarbons are thermally broken down into smaller and useful molecules

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10
Q

What type of reaction is cracking?

A

Thermal decomposition

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11
Q

What are the conditions for cracking

A

Reactant heated to vapor, passed over a hot catalyst (Catalytic cracking)

heated to vapour, mixed with steam and heated to high temperatures (steam cracking)

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12
Q

How are the products of cracking used?

A

The products are alkenes and alkanes-used as polymers and starting materials for synthesis,like petrol

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13
Q

What is the test for alkenes

A

Add bromine water. Colour change occurs from orange to colourless

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14
Q

Describe the combustion of alkenes

A

They burn with smoky fames due to incomplete combustion

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15
Q

Describe the reactions of alkenes

A

Addition atoms across the carbon-carbon double bond so that the double bond becomes a single carbon-carbon bond.
a)With hydrogen-hydrogenation: requires a higher temperature and a nickel catalyst
b)With steam-hydration: requires high temperature, pressure and concentrated phosphoric acid (H3PO4) as a catalyst.
c)With Br2/Cl2/I2-addition on halogens

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16
Q

What is an alcohol?

A

An organic compound that contains an -OH functional group

17
Q

State characteristics of methanol, ethanol, propanol and butanol.

A

-Dissolve in water to form a neutral solution
-React with sodium to form hydrogen
-Burn in oxygen
-React with carboxylic acids in presence of acid catalyst to form esters.

18
Q

Oxidation of the alcohol leads to…?

A

Carboxylic acids

19
Q

What are some uses of alcohols?

A

Fuels, solvents, drinks

20
Q

State the conditions requires for fermentation of glucose and state the equation of the reaction

A

30 degress Celcius, aqueous solution of the glucose, absence of air, yeast added
-C6H12O6→2C2H5OH+2CO2

21
Q

What are carboxylic acids?

A

Organic compounds that contain a -COOH functional group

22
Q

WHat is a functional group?

A

a group of atoms responsible for the characteristic reactions of a particular compound.

23
Q

State characteristics of carboxylic acids

A

-Dissolve in water to form an acidic solution (H+ ions)
-React with metal carbonates to form Carbon dioxide,water and a salt
-Reacts with alcohols with an acid catalyst to produce esters
-React with metals to give off hydrogen gas

24
Q

What type of acid is carboxylic acid?

A

Weak acid

25
Q

Explain why carboxylic acids are weak acids?

A

They are partially dissociated in water, thus the pH of carboxylic acid in solution is not as low as a solution of a strong acid of the same concentration

26
Q

What is an ester and how is it formed?

A

An organic compound containing a -COO- functional group, formed from carboxylic acid and alcohol in presence of a sulfuric acid catalyst. Fruity smell.

27
Q

What is a polymer? How do molegules containing C=C bond form together?

A

A polymer is a long chain molecule which is ade by lots of smaller molecules joining together. C=C bonds open up and many smaller molecules (monomers), join together to form a chain (a polymer). No other products are made. It is called an addition polymerisation reaction.

28
Q

Give 3 examples of addition polymers and their uses

A

Polyethene-blastic bags
Polytetrafluorethene-teflon surfaces
Polychloroethene(PVC)-water pipes

29
Q

What is a repeating unit of a polymer?

A

It is the smallest structure which yields the structure of the polymer
In addition polymers to draw it, take a monomer, change C=C to C-C and she additional single bonds extending away from these carbons

30
Q

What is a condensation polymer?

A

A polymer made in condensation polymeration. In this reaction many molecules join together, the polymer is formed but also a small molecule is released, eg. H20, HCl. Polyesters+Polyamides

31
Q

What is the arrangement of C-H bonds in methane

A

Tetrahedral

32
Q

Why are alkenes considered unreactive

A

They exclusively contain relatively strong C-C and C-H bonds which are hard to break

33
Q

Alkanes can undergo halogenation reactions. Describe the process

A

This reaction involves substituting hydrogen atoms with halogen atoms in the alkane molecule. It reacquire UV radiation. This radiation breaks up the halogen molecules atom (Cl2 = 2 Cl)

34
Q

How can ethanol be oxidised? What ar the products?

A

a) hEating with acidified (H2SO4), orange potassium dichromate (IV) solution leads to oxidation to ethanoic acid, CH3COOH. The solution turns green over the course of the reaction. (reduction of Cr(IV) to Cr3+)

b)Microbial oxidation. Ethanol is exposed to air, it will slowly be oxidised to ethanoic acid with the help of bacteria

35
Q

What are isomers?

A

Isomers are compounds of the same molecular formula having different structural formulae

36
Q

Addition polymerisation requires an additive-whats its name and the role?

A

An initiator: chemical that initiates the addition polymerisation by helping one of the C=C bonds to break

37
Q

What are biopolyesters?

A

Special type of polyesters that degrade upon prorogued exposure to microbes, O2 and water (contrary to normal polyesters, which are resistant to decomposition under these conditions).

38
Q

Starting points to name alkanes and alkenes depending on the num of carbon molecules

A

1- Meth
2- Eth
3- Prop
4- But
+Rest are like shapes

iGCSE Chemistry (5 decks)

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