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Organic Chemistry Flashcards

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1
Q

What’s a hydrocarbon?

A

A compound containing only the elements hydrogen and carbon

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2
Q

What’s saturated?

A

An organic compound in which all the bonds are single bonds

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3
Q

What’s unsaturated?

A

An organic compound that contains a carbon-carbon double bond

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4
Q

What’s a general formula?

A

A formula that states the ratio of atoms of each element in the formula of every compound in a particular homologous series

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5
Q

What’s the general formula of alkenes?

A

CnH2n

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6
Q

What’s isomerism?

A

Compounds that have the same molecular formula but different displayed formulae are said to exhibit isomerism. (The different compounds are called isomers)

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7
Q

What’s the general formula of alkanes?

A

CnH2n+2

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8
Q

What are the products of complete and incomplete combustion of alkanes?

A

Alkane + oxygen —> carbon dioxide + water (+ energy) ➡️ Gas burns with clean blue flame

Eg methane;
CH4 + 2O2 —> CO2 + 2H2O

If not enough oxygen:
Alkane + oxygen —> carbon + carbon monoxide + carbon dioxide + water (+ energy) ➡️ smoky yellow flame, less energy than complete combustion

4CH4 + 6O2 —> C + 2CO + CO2 + 8H2O

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9
Q

Describe the substitution reaction of methane with bromine to form bromomethane in the presence of UV light;

A

Halogens react w/ alkanes in the presence of ultraviolet light (to make haloalkanes)

In these reactions a hydrogen atom from the alkane is substituted/replaced by chlorine or bromine. (This is called a substitution reaction)

Eg.

Methane + bromine —> bromomethane + hydrogen bromide

H                 (UV)     Br H-C-H  + Br2   —>  H-C-H + HBr
H                             H
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10
Q

Describe the addition reaction of alkenes w/ bromine;

A

Halogens react w/ alkenes to make haloalkenes

In these reactions, the C=C double bond is split and a halogen atom is added to each of the carbons. (This is called an addition reaction)

Eg.

Ethene + bromine —> dibromoethane

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11
Q

How can one test for carbon-carbon double bonds?

A

The reaction between bromine and alkenes is often used as a test for carbon-carbon double bonds (alkenes)

When you shake in a test tube: an alkene with orange bromine water ➡️ the solution becomes colourless - this is because the bromine molecules, which are orange, are reacting with the alkene to make a dibromoalkene, which is colourless

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12
Q

Describe manufacture of ethanol w/ ethene and steam;

A

Passing ethene C2H4 and steam H2O over a phosphoric acid catalyst (will make steam and ethene react) to make ethanol.

Temp of 300 degrees C and pressure of 60-70 atmospheres

  • CONTINUOUS process - expensive equipment but low labour costs.
  • Produced pure
  • Very fast reaction
  • Ethene from oil is a finite resource (crude oil is a non-renewable resource - which will start running out soon so will become v expensive)

C2H4 + H2O —> C2H5OH

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13
Q

Describe manufacture of ethanol by fermentation of sugars;

A

Raw material for fermentation is sugar eg glucose. This is converted into ethanol using yeast.

Temp of 30 degrees C
Simpler equipment than using ethene

  • BATCH process - cheap equipment, high labour costs
  • Very impure ethanol produced - needs to be distilled to increase its strength and purified
  • Raw material sugar (sugar cane) is renewable
  • very slow reaction
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14
Q

Describe the dehydration of ethanol to form ethene;

A

Turn ethanol back into ethene by removing water from the ethanol in a dehydration reaction (ie elimination of water).

Ethanol vapour is passed over a hot catalyst of aluminium oxide Al2O3 - the catalyst provides a last surface area for the reaction.

C2H5OH —> C2H4 + H2O

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15
Q

How can the pH scale be used to classify solutions as acidic/alkaline/neutral?

A

Goes from 0 to 14. The strongest acid has pH 0.
Strongly acidic pH 0-3 (car battery acid, vinegar, lemon juice)
Weakly acidic pH 4-6. (Normal rain pH 5/acid rain pH4)

Neutral substance has pH 7 (eg pure water)

The strongest alkali has ph 14.
Weakly alkaline pH8-11 (washing up liquid, pancreatic juice) strongly alkaline pH 12-14 (bleach, caustic soda-drain cleaner)

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16
Q

What’s an indicator?

A

A dye that changes colour depending whether it’s above or below a certain pH

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17
Q

How can one use litmus indicator?

A

Litmus paper tests whether a solution is acidic or alkaline because it changes colour at about pH 7.

It’s red in acidic solutions, purple in neutral, blue in alkaline solutions

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18
Q

How can one use phenolphthalein as an indicator?

A

Phenolphthalein will change from colourless in acidic solutions to bright pink in alkaline solutions.

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19
Q

How can one use methyl orange as an indicator?

A

Methyl orange changes from red in acidic solutions to yellow in alkaline solutions.

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20
Q

How can one use universal indicator to measure the approximate pH value of a solution?

A

Universal indicator is a v useful combination of dyes which gives the colours of the pH scale.

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21
Q

Acids are a source of…

A

hydrogen ions, H+

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22
Q

Alkalis are a source of…

A

hydroxide ions, OH-

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23
Q

How can acids be neutralised by bases?

A

Alkalis are soluble bases. a base is a substance that can neutralise an acid. When an acid and a base react/acid and alkali = neutralisation (products are neutral - pH7)

acid + base —> salt + water

Or

H+ (aq) + OH- (aq)—> H2O (l)

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24
Q

What’s a homologous series?

A

A series of organic compounds that have the same general formula, similar chemical reactions and where each member differs from the next by a —CH2— group

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25
Q

What are the general rules for predicting solubility of salts in water;

A
  • sodium, potassium, ammonium salts are soluble
  • nitrates are soluble
  • most chlorides are soluble — except silver chloride
  • most sulfates are soluble — except barium sulfate, calcium sulfate

• most carbonates are insoluble — except sodium, potassium, ammonium carbonates

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26
Q

Acids react with metal oxides to make what?

A

Metal oxides are generally bases. (They’ll react with acids to form a salt and water)

Acid + Metal Oxide —> Salt + Water

• If the acid is hydrochloric acid, the salt will be a metal chloride eg

Hydrochloric acid + copper oxide —> copper chloride + water

2HCl + CuO —> CuCl2 + H2O

• If the acid is sulfuric acid, the salt will be a metal sulfate eg

Sulfuric acid + zinc oxide —> zinc sulfate + water

H2SO4 + ZnO —> ZnSO4 + H2O

• If the acid is nitric acid, the salt will be a metal nitrate eg

Nitric acid + copper oxide —> copper nitrate + water

2HNO3 + CuO —> Cu(NO3) + H2O

27
Q

Acids react with metal carbonates to make what?

A

Acid + Metal Carbonate —> Salt + Water + Carbon Dioxide (so you’ll see bubbles)

Hydrochloric acid + sodium carbonate —> sodium chloride + water + carbon dioxide

2HCl + Na2CO3 —> 2NaCl + H2O + CO2

Sulfuric acid + calcium carbonate —> calcium sulfate + water + carbon dioxide

H2SO4 + CaCO3 —> CaSO4 + H2O + CO2

Nitric acid + calcium carbonate —> calcium nitrate + water + carbon dioxide

2HNO3 + CaCO3 —> Ca(NO3)2 + H2O + CO2

28
Q

Acids react with metals to make what?

A

Acid + Metal —> Salt + Hydrogen

Hydrochloric acid + magnesium —> magnesium chloride + hydrogen

Sulfuric acid + magnesium —> magnesium sulfate + hydrogen

29
Q

Describe an experiment to prepare soluble salts from acids;

A

• Need to pick the right acid, plus an insoluble base (most metal oxides/carbonates/hydroxides are insoluble)

Eg to make copper nitrate, mix nitric acid and copper carbonate

CuCO3 (s) + 2HNO3 (aq) —>
Cu(NO3)2 (aq) + CO2 (aq) + H2O (l)

  • add the metal oxide/carbonate/hydroxide to acid — the solid will dissolve in the acid as it reacts. You’ll know when all the acid has been neutralised bc excess solid will sink and remain at bottom
  • filter out excess base to get salt solution. (To get pure, solid crystals of the salt, evaporate off the water)
30
Q

Describe an experiment to prepare insoluble salts using precipitation reactions;

A
  • pick two solutions that contain the ions you need. eg to make barium sulfate (which is insoluble) you need a solution which contains barium ions and one which contains sulfate ions.
  • so you can mix barium chloride (most chlorides are soluble) with sulfuric acid.

BaCl2 (aq) + H2SO4 (aq) —> BaSO4 (s) + 2HCl (aq)

31
Q

What’s a precipitation reaction?

A

Mix the two solutions containing the ions that you need.

32
Q

Describe experiments to carry out acid-alkali titrations:

A
  • using a pipette and pipette filler, add some alkali (about 25cm3) to a conical flask, along w/ two or three drops of indicator.
  • fill burette with the acid below eye level. Using burette, add the acid to alkali a bit at a time- giving the conical flask a regular swirl. (Slowly towards the end-point - colour change)
  • indicator changes colour when all the alkali has been neutralised. eg phenolphthalein is pink in alkalis, colourless in acids.
  • record the volume of acid needed to neutralise the alkali
  • repeat - make sure to get roughly the same result each time - more reliable
33
Q

What do titrations allow you to do?

A

Allow you to find out exactly how much acid is needed to neutralise a quantity of alkali (or vice versa)

34
Q

What’s exothermic?

A

Chemical reactions in which heat energy is given out

35
Q

What’s endothermic?

A

Chemical reactions in which heat energy is taken in

36
Q

Describe calorimetry experiment for combustion;

A

To measure amount of energy produced when a fuel is burnt, simply burn the fuel and use the flame to heat up some water.

  • Make us much heat as possible go into heating up the water. Reducing draughts is key - use a screen to act as a draught excluder, don’t do it near window
  • 50g of water in copper can (conducts heat so well) and record temp
  • weigh the spirit burner and lid
  • put the spirit burner underneath the can, and light the wick. Heat the water, stirring constantly, until the temp reaches about 50 degrees.
  • put out the flame using the burner lid and measure the final temp
  • weigh spirit burner and lid again

4.2 x temp rise x mass of water (50g)
= energy produced in experiment.

Energy divided by mass of spirit burnt = how much energy 1 g of spirit produces

37
Q

What’s calorimetry?

A

Allows you to measure the amount of energy transferred in a chemical reaction.

38
Q

What’s specific heat capacity of water?

A

Amount of energy needed to raise the temp of 1 gram of water by 1 degree (4.2 j/g/c)

It takes 4.2 joules of energy to raise the temp of 1 g of water by 1 C

39
Q

Describe calorimetry experiment for dissolving, displacement, and neutralisation reactions:

A
  • add acid into polystyrene cup, record temp. add alkali into measuring cylinder and record temp. Add to each other and stir. Take temp of mixture every 30 secs and record highest temp reached
  • big problem - amount of energy lost to surroundings (reduce by putting polystyrene cup into a beaker of cotton wool to give more insulation, and put a lid on the cup to reduce energy lost by evaporation)
40
Q

How to calculate MOLAR enthalpy change from heat energy change.

A

molar enthalpy change = enthalpy change given out by one mole of the reactant.

Amount of energy produced = in J

Mr of maths = 44.6

Moles = g/Mr =
mass of meths burnt/44.6

heat produced by one mole =
energy produced in the reaction (negative sign if exothermic)/ moles

41
Q

How to calculate enthalpy change?

A

4.2 x mass of water x temp rise = ΔH

42
Q

ΔH to represents what?

A

ΔH is the symbol that represents the amount of energy lost or gained in a reaction.

(+ΔH is endothermic bc it gains heat)
(-ΔH is exothermic bc it loses heat)

43
Q

Breaking bonds is what?

A

Breaking bonds requires energy, takes in heat - Endothermic.

44
Q

Making bonds is what?

A

Making bonds releases energy, gives out heat - Exothermic.

45
Q

How to calculate bond energys

A

Enthalpy change = total energy absorbed to break bonds - total energy released in making bonds

46
Q

What does rate of reaction depend on?

A

Temperature
Concentration (or pressure for gases)
Catalyst
Size of particles (or surface area)

47
Q

What’s activation energy?

A

Represents the minimum energy needed by reacting particles for the reaction to occur.

On a diagram: to the top and then to the products (or with catalyst- to below top, then products)

48
Q

Describe an experiment to investigate the effect of changes in surface area on the rate of reaction:

A
  • conical flask w/ bung and dilute hydrochloride acid and marble chips inside. gas syringe connected by glass tube to inside of flask.
  • measure vol of gas evolved w/ a gas syringe and take readings at regular intervals
  • make table of readings, plot on graph. Time is independent variable (x) and volume is dependent variable (y)
  • repeat with same volume of acid, same mass of marble chips, but more crunched up.
  • repeat with same mass of powdered marble instead of marble chips
49
Q

Describe an experiment to investigate the effect of changes in concentration on the rate of reaction:

A
  • conical flask w/ dilute HCl and magnesium metal.
  • reaction gives off hydrogen gas, which we can measure with mass balance
  • take readings of mass at regular intervals. Put results in table, and work out loss of mass for each reading. Plot graph
  • time is the independent variable and mass loss the dependent variable.
  • repeat w/ more concentrated acid solutions, ALWAYS SAME amount of magnesium
  • volume of acid must always be kept the same too - only conc increased.
50
Q

Describe an experiment to investigate the effect of changes in temperature on the rate of reaction:

A
  • sodium thiosulfate and HCl produce a cloudy precipitate. Both clear solutions that react together to form a yellow precipitate of sulfur.
  • Put concical flask containing sodium thiosulfate on top of paper with black cross. Add HCl and immediately start stop watch to how long it takes for black mark to disappear through the cloudy sulfur.
  • repeat for solutions at different temperature. Use a water bath to heat both solutions at the right temp before mixing them.
  • depth of liquid same each time, same person judging when black cross disappears.

(Can use this for concentration)

No graph, only table of results. As temp increases, time decreases.

51
Q

Describe an experiment to investigate the effect of using a catalyst on the rate of reaction:

A

• decomposition of hydrogen peroxide:

2H2O2 (aq) —> 2H2O (l) + O2 (g)

  • conical flask w/ hydrogen peroxide in it and a bung with a gas syringe connected by glass tube.
  • decomposition of hydrogen peroxide is usually quite slow but sprinkle catalyst of MANGANESE (IV) OXIDE speeds it up. (Other catalysts that work are found is blood/potato peel)
  • oxygen given off, ideal way to measure rate of reaction using gas syringe (bubbles)

(Can be used to measure affects of temp or conc of H2O2)

52
Q

Describe the effects on rate of reaction of changes in surface area:

A
  • an increase in SA, particles around it in the solution have more area to work on - causes more frequent collisions, so rate is faster.
  • the extra surface area gives a quicker reaction, there is also more gas evolved/produced overall (as long as acid is in excess)
53
Q

Describe the effects on rate of reaction of changes in temperature:

A

Higher temp, particles have more energy, move faster and collide more frequently

54
Q

Describe the effects on rate of reaction of changes in concentration:

A
  • the higher the concentration, more particles of reactant knocking between water molecules - collisions between important molecules more likely.
  • higher pressure in a gas - particles closer together - collide more frequently

In the experiment - the faster the loss in mass (faster the rate of reaction- steeper graph)

As the reaction progresses, fewer and fewer reactant particles so they collide less frequently, rate slows down

55
Q

Describe the effects on rate of reaction of using a catalyst:

A

• a catalyst gives the reacting particles a surface to stick to, increasing the number of successful collisions by lowering activation energy

(better catalysts - quicker reaction - steeper levels on graph.)

56
Q

How does a catalyst work?

A

A catalyst makes reaction faster by providing an alternate pathway with a lower activation energy

Lower curve on diagram - less initial energy is needed for reaction to begin.

ΔH; overall energy change for the reaction remains the same.

57
Q

Describe the dehydration of hydrated copper (I) sulfate:

A

(Copper (II) sulfate crystals can be used as a test for water- it water is present in the thing you tested by adding it to the White powder, it will turn into blue crystals)

Add a couple of drops of water to white powder copper (II) sulfate to forms blue crystals

If you heat the blue copper (II) sulfate crystals it drives the water off, leaving white anhydrous copper (II) sulfate powder.

58
Q

What’s a reversible reaction?

A

A reversible reaction is one where the products of the reaction can react to produce the original reactants.

59
Q

Describe the effect of head on ammonium chloride:

A

The thermal decomposition of ammonium chloride is reversible.

Ammonium chloride is a white solid. When heated it breaks down into the gases ammonia and hydrogen chloride. (Forward reaction)

If you let ammonia and hydrogen chloride cool, it reacts to re-form the solid. This is the backwards reaction.

60
Q

What’s dynamic equilibrium?

A

If a reversible reaction takes place in a closed system (none of reactants or products can escape), then dynamic equilibrium will be reached

Dynamic equilibrium - reactions are still taking place in both directions, but there’s no overall effect because forward and backwards reactions are taking place at the same rate.

61
Q

What’s equilibrium?

A

The relative quantities of reactants and products will reach a certain balance and stay there.

62
Q

What happens if you change the pressure in a reversible reaction?

A

If you raise the pressure, it will encourage the reaction which produces fewer molecules of gas (the position of equilibrium favours the side with less molecules)

If you lower the pressure, it will encourage the reaction which produces more molecules of gas (the position of equilibrium favours the side with more molecules)

63
Q

What happens if you change the temp in a reversible reaction?

A

If you raise the temperature, the endothermic reaction will increase to use up the extra heat. (PoE will favour the endothermic reaction)

If you reduce the temperature, the exothermic reaction will increase to give out more heat. (PoE will favour the Exothermic reaction)

Chemistry (7 decks)

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