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A-Level Chemistry > equations//reactions > Flashcards

equations//reactions Flashcards

1
Q

Metal + acid –>

A

Metal salt + H^2

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2
Q

Metal + water –>

A

Metal hydroxide + H^2

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3
Q

Metal carbonate + acid –>

A

Metal salt + carbon dioxide + water

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4
Q

How many moles are there in 12g of carbon-12?

A

n = m / Mr

= 12g / 12g/mol

= 1 mole

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5
Q

How many atoms are there in 2 moles of carbon-12?

A

No. of atoms = N~A * n

= (6.02 10^23) 2

= 1.204 * 10^24 atoms

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6
Q

If 2H~2 and CO~2 are products and hydrogen is useful, what is the atom economy?

A

“Mr of all = 48
Mr of 2H~2 = 4

Atom economy = (4 * 100%) / 48 = 8.33%

Atom economy is 8.33%”

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7
Q

The mass of CuSO~4.xH~2O = 6.8g and the mass of anhydrous CuSO~4 = 4.35g. Find x

A

xH~2O = 6.8g - 4.35g = 2.45g

N = m / Mr is used for the CuSO~4 and the H~2O

Water = 0.1361 mol
Anhydrous salt = 0.027 mol

Ratio of anhydrous salt to water = 1:5

CuSO~4 + 5H~2O

x = 5

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8
Q

What volume is taken up by 10 mol of CO~2?

A

“N = V / 24

V = 24N

V = 24 dm^3 mol^-1 * 10mol

V = 240 dm^3”

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9
Q

Find the volume of 64g of O~2 gas

A

“2 formulas are needed here

N = m / Mr = 64g / 32

2 moles of oxygen gas

V = 24N

V = 24 * 2

V = 48dm^3”

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10
Q

“SiCl~4 + 2H~2O

There is 5g of SiCl~4.

Find the mass of the 2H~2O”

A

“The ratio of moles from SiCl~4 to 2H~2O is clearly 1:2 due to the amount of molecules

N = m / Mr = 5g / 170.1 = 0.0294

Number of SiCl~4 moles = 0.0294 mol

Using the ratio, 2H~2O has 2 times more moles than SiCl~4

0.0294 * 2 = 0.0588

There are 0.0588 mol of water”

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11
Q

What temperature gives a molar volume of 24dm^3 mol^-1?

A

“P = 101kPa (as usual) = 101000Pa

V = 24dm^3 = 0.024m^3

n = 1 mol

R = 8.314

PV = nRT

T = PV / nR

T = (101000 0.024) / (1 8.314)

T = 291.6K”

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12
Q

Find the concentration of 0.0032 mol of HCl dissolved in 250cm^3

A

“n = 0.0032 mol

V = 250cm^3 = 0.25dm^3

n = c * V

c = n / V

c = 0.0032 / 0.25

c = 0.128 mol dm^-3”

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13
Q

“Find the mass of KOH needed to prepare 250cm^3 of a 0.2mol dm^-3 solution

The Mr of KOH = 56.1”

A

“V = 0.25dm^3

c = 0.2 mol dm^-3

n = c * V

n = 0.25 * 0.2

n = 0.05mol

m = n * Mr

m = 0.05 * 56.1

m = 2.805g”

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14
Q

“2NaOH + H~2 SO~4

Acid volume = 0.02365dm^3

Alkali volume = 0.025dm^3

Alkali concentration = 1.25 mol dm^-3

Calculate the concentration of the acid”

A

“n of alkali = c V = 0.025 1.25
= 0.03125 mol

2 alkali molecules and 1 acid molecule
Ratio = 2:1

n of acid = n of alkali / 2 = 0.03125 / 2
= 0.015625 mol

So c of acid = n / V = 0.015625 mol / 0.02365 dm^3
= 0.6607 mol dm^-3

Concentration of acid is 0.6607 mol dm^-3”

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15
Q

“A solution contains 0.564g of CaCl~2 in 250 cm^3 of water

Find the mass concentration
“

A

“Mass concentration = 0.564g / 0.25dm^3

= 2.26 g dm^-3”

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16
Q

“A solution of NaOH has a concentration of 0.25 mol dm^-3

Calculate the mass concentration”

A

“Mass concentration = 0.25 * 38

= 9.5 g dm^-3”

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17
Q

How do the 4 main acids dissociate?

A

“H~2 SO~4 –> 2H+ + SO~4 2-

HCl –> H+ + Cl-

HNO~3 –> H+ + NO~3-

CH~3 COOH –> H+ + CH~3 COO-“

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18
Q

How many chlorine ions surround each sodium ion and how many sodiums surround each chlorine in sodium chloride?

A

“6 sodium around each chlorine

6 chlorine around each sodium”

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19
Q

How would you draw water in 3D?

A

“It has 2 bonded pairs and 2 lone pairs

So it is non-linear

Draw with an O in the middle

Show 2 hydrogens with a 104.5 bond angle

Also draw the 2 lone pairs”

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20
Q

What is the polarity of a C-H bond? You need to remember this

A

“Non-polar

Unusual as it seems”

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21
Q

What is the IMF for HCl?

A

“Permanent dipole-dipole forces

You have to remember this”

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22
Q

“Describe and explain how electrical conductivity in mercury bromide and in mercury in both solid and molten states

5 marks”

A

“HgBr~2 conducts when molten but not when solid

Because ions are free to move in molten state

But ions are in a FIXED LATTICE in solid state

Mercury conducts in both states

Because delocalised electrons carry charge in both states”

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23
Q

“There are 3 carbons in the chain

There is a chlorine on the first and second carbon

Name this organic”

A

“The base alkane is propane

So it is called:

1, 2 - dichloropropane”

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24
Q

“The base alkane is ethanol

If there are 3 bromines on one of the carbons

What is the name of this organic?”

A

1, 1, 1 - tribromoethane

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25
Q

If there are 4 halogens on an organic, what is the prefix used before the halogen name?

A

Tetra

E.g 1, 2, 3, 4 - tetrafluorobutane

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26
Q

“What are the 3 structural isomers of C~5 H~12?

Give their names and structural formulas”

A

“Pentane
CH~3 (CH~2)~3 CH~3

2-methylbutane
CH~3 CH(CH~3) CH~2 CH~3

2,2-dimethylpropane
C(CH~3)~4”

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27
Q

What are the 5 structural isomers of C~6 H~14?

A

“Hexane

2-methylpentane

3-methylpentane

2, 2-dimethylbutane

2, 3-dimethylbutane”

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28
Q

What are the 2 structural isomers for C~3 H~7 Cl?

A

“1-chloropropane

2-chloropropane
“

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29
Q

What is the combustion equation for hexane?

A

“C~6 H~14 + 9.5O~2
–>
6CO~2 + 7H~2 O

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30
Q

What is the incomplete combustion of pentane?

A

“C~5 H~12 + 5.5O~2
–>
5CO + 6H~2 O

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31
Q

What is the complete combustion of propanol?

A

“C~3 H~8 O + 4.5O~2
–>
3CO~2 + 4H~2 O”

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32
Q

“What do you have to always remember in combustion of alcohols?

A

Don’t forget that there is always one oxygen on the LHS when you try to balance it

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33
Q

How is homolytic fission shown in an equation?

A

“H~3 C-CH~3
–>
H~3 C• + •CH~3

The 2 products are radicals”

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34
Q

“How do you write an equation for heterolytic fission?

“

A 
"H~3 C-Cl 
-->
H~3 C+
\+
Cl-"
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35
Q

Show the addition reaction of but-2-ene and water

A

“C~4 H~8 + H~2 O –> C~4 H~10 O

Butan-2-ol is formed”

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36
Q

What are the initiation, propagation and termination stages of CH~4 + Br~2?

A

Initiation:
Br~2 –> Br• + Br•

Propagation:
CH~4 + Br• –> CH~3• + HBr

CH~3• + Br~2 –> CH~3 Br + Br•

Termination:
Br• + Br• –> Br~2

CH~3• + CH~3• –> C~2 H~6

CH~3• + Br• –> CH~3 Br

This works for any alkane and any halogen

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37
Q

Show how chlorine and ethane can react to form a molecule with 4 carbon atoms

A

Initiation:
Cl~2 –> Cl• + Cl•

Propagation:
C~2 H~6 + Cl• –> C~2 H~5 + HCl

Termination:
C~2 H~5• + C~2 H~5• –> C~4 H~10

This isn’t all of the possible stages but only the ones needed to make C~4 H~10

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38
Q

Show how oxygen gas forms ozone

A

“O~2 –> 2O•

O~2 + O• O~3”

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39
Q

What is the general equation for how ozone is removed?

A

O~3 + O –> 2O~2

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40
Q

“Show how CFCs remove ozone

“

A

“Initiation:
CF~2 Cl~2 –> Cl• + CF~2 Cl

Propagation:
Cl• + O~3 –> ClO• + O~2
ClO• + O –> Cl• + O~2

Overall:
O~3 + O –> 2O~2

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41
Q

Show how NO• removes ozone

A

We don’t need to know initiation here

Propagation:
NO• + O~3 –> NO~2• + O~2

NO~2• + O –> NO• + O~2

Overall:
O~3 + O –> 2O~2

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42
Q

What is the reaction from hexane to cyclohexane?

A

“C~6 H~14 –>

C~6 H~12 + H~2”

43
Q

How do you draw the stereoisomers of 2-methylbut-2-ene?

A

“One of the double bonded carbons has the same group bonded to it twice

This means that 2-methylbut-2-ene doesn’t have stereoisomers”

44
Q

How do you test for alkenes and cycloalkenes?

A

“Add bromine water

If it is an alkene or cycloalkene

The bromine water will turn from orange to colourless”

45
Q

What is the reaction for bromine water added to alkenes?

A

“Example:

Ethene + Bromine –> 1,2-dibromoethane”

46
Q

What is the reaction between cyclohexene and fluorine?

A

They make 1,2-difluorocyclohexane

47
Q

“How is margarine made?

A

Hydrogenation of plant oils

48
Q

“Which products are made with the reaction between but-1-ene and HCl?

Which one is favoured?”

A

“1-chlorobutane
2-chlorobutane

2-chlorobutane is favoured”

49
Q

How do you draw the addition polymerisation of poly(propene)?

A

Do the whole thing but only draw the double bond part as displayed and draw the CH~3 coming off a bond

Do the same for the polymer side of the equation

50
Q

If the exam wants you draw “3 repeat units of poly(propene)”, what do you draw?

A

“Draw 3 repeat units in a chain bonded together

Draw brackets around this and show the bonds going through the brackets”

51
Q

What are the reagents and conditions for electrophilic addition of alkenes?

A

“Steam

Acid catalyst”

52
Q

What is the enthalpy change of the thermal decomposition of calcium carbonate?

A

+ 178 kJ mol^-1

53
Q

“What is the standard formation equation of ammonia

“

A 
"0.5 N~2 (g)
\+
1.5 H~2 (g)
-->
NH~3 (g)

You would then probably have to write the standard enthalpy change of formation afterwards”

54
Q

“What is the density of water / a solution?

“

A

“1 g cm^-3

Remember that it is grams and centimetres”

55
Q

Show the enthalpy change combustion reaction for ethane

A

“C~2 H~6 + 3.5O~2
–>
2CO~2 + 3H~2 O”

56
Q

Describe the practical experiment for determination of enthalpy change of combustion

A

“Measure a known volume of water into a beaker

Weigh the burner containing fuel

Take initial temp of water

Burner is lit and water heated until temperature has risen by a reasonable amount

Final temperature is taken

The burner is weighed to find mass of fuel burnt”

57
Q

“Do alcohols dissolve in water?

Explain”

A

“They do dissolve in water

Because they are polar due to their hydrogen bonds”

58
Q

“In the oxidation of alcohols

What is the oxidising agent?

A

“Acidified potassium dichromate

H+ | K~2 Cr~2 O~7

59
Q

“How do you write the equation for the oxidation of an alcohol by distillation?
“

A

“Draw out the alcohol

Then put + [O]

Then draw the reaction arrow with H+ | K~2 Cr~2 O~7 above it and “distillation” below it

Draw the aldehyde with the same number of carbons as the alcohol

Then put + H~2 O”

60
Q

“What are the observations of all primary alcohol oxidation reactions?

A

“Acidified potassium dichromate goes from orange to green

61
Q

“How do you write the equation for reflux oxidising alcohols?
“

A

“Draw the alcohol

Put + 2[O]

Draw the reaction arrow with H+ | K~2 Cr~2 O~7 above and reflux below

Draw the carboxylic acid

Write + H~2 O”

62
Q

What is the observation when oxidising secondary alcohols?

A

Still colour change from orange to green

63
Q

How do you write the reaction for oxidation of secondary alcohols?

A

“Draw an alcohol where the OH isn’t on an end carbon

Put + [O]

Put a reaction arrow with H+ | K~2 Cr~2 O~7 above it and “heat” below it

Draw the ketone

Put + H~2 O

64
Q

Describe the dehydration of alcohols

A

“An alcohol is heated with a reagent of CONCENTRATED H~2 SO~4 and heat

An alkene and water is produced

This is an elimination reaction

65
Q

With dehydration of alcohols, what is different when secondary alcohols are used?

A

“2 different alkenes are produced

With the double bond on the left of where the OH was

And with the double bond on the right of where the OH was

66
Q

What are the conditions and reagents of alcohol substitution? (Where an OH is replaced by a halogen)

A

“Reflux the alcohol

With sulphuric acid and sodium halide

(The halide contains the halogen that we want in the haloalkane)

67
Q

Why is a sodium halide used in substitution of alcohols?

A

The hydrogen halide on its own doesn’t work for some reason

68
Q

What is the first reaction which happens in substitution of alcohols?

A

“NaX + H~2 SO~4
–>
NaHSO~4 + HX

Where X is the halogen”

69
Q

“What is the second reaction which happens in substitution of alcohols?

Use ethanol as the alcohol”

A

“C~2 H~6 O + HX
–>
C~2 H~5 X + H~2 0

Where X is the halogen”

70
Q

“What is the overall reaction of alcohol substitution?

Use propanol as the alcohol and chlorine as the halogen”

A

“C~3 H~8 O + NaCl + H~2 SO~4
–>
C~3 H~7 Cl + NaHSO~4 + H~2 O”

71
Q

“Why are the boiling points of branched alcohols less than boiling points of straight chain alcohols?

2 marks”

A

“Less points of contact between branched alcohols

So less energy required to break London forces in branched alcohols”

72
Q

“What happens to do with dipoles in haloalkanes?

“

A

“The X gets a delta -

The C attached to it gets a delta +

Due to a significant electronegativity difference”

73
Q

“What are the hydrolysis conditions and reagents?

A

“Hot aqueous sodium / potassium hydroxide

A reflux

74
Q

“What is the overall reaction of hydrolysis?

For C~3 H~7 Cl as the haloalkane:

A

“C~3 H~7 Cl + OH-
–>
C~3 H~8 O + Cl-“

75
Q

What are the reagents used to measure rate of hydrolysis of primary haloalkanes?

A

“Water

AgNO~3

Ethanol”

76
Q

What is the ionic equation for silver and halide ions in rate of hydrolysis?

A

Ag+ + X- –> AgX

77
Q

What is the overall rate hydrolysis equation?

A

“Haloalkane + water + AgNO~3
–>
Alcohol (from haloalkane) + HNO~3 + AgX

AgX is the precipitate formed “

78
Q

“What is the difference between the rate of hydrolysis of a flouroalkane compared to a iodoalkane and why?

A

C-I bonds are weaker than C-F bonds due to having lower bond enthalpy

So the rate of hydrolysis of the iodoalkane is greater than the flouroalkane

79
Q

“Give the 5 steps of mass spectrometry

A

“Injection of the sample of molecules as a gas

Ionisation by a electron gun which knocks off electrons from outer shells

Acceleration of positive ions towards electromagnet

Deflection by the electromagnet to change direction of ions

Detection of the different ions and their abundances”

80
Q

“List all the Quickfit apparatus needed in reflux

5 items needed”

A

“Pear-shaped flask

Receiver

Screw-tap adaptor

Condenser

Still head”

81
Q

What are the actual values for the temperature and pressure of the Haber process?

A

“350 - 500 C temperature

100 - 200 atm (atmospheres) pressure”

82
Q

What percentage of reactants in the Haber process are turned into ammonia?

A

Only 15% of reactants

83
Q

What is the chemical equation showing lithium being ionised?

A

“Li(g) –> Li(g)+ + e-

The gas state symbols are very important”

84
Q

What is the reaction for the redox displacement of chlorine and bromide?

A

“Cl~2 + 2Br-
–>
2Cl- + Br~2”

85
Q

What are the colours of the different halogens in both water and cyclohexane?

A

“Solution in water:

Cl~2 is pale green
Br~2 is orange
I~2 is brown

Solution is cyclohexane:

Cl~2 is pale green
Br~2 is orange
I~2 is violet

Notice that only the iodine changes colour from water to cyclohexane

86
Q

“How do you do halide tests?

(Different to redox displacement)”

A

“Dissolve halide in water

Add aqueous silver nitrate

Silver halide precipitate is formed and its colour tells us what the halide is”

87
Q

“In halide tests

What are the precipitate colours for the different halides?”

A

“Chloride gives white

Bromide gives cream

Iodide gives yellow”

88
Q

“How do you confirm the halide test result?

“

A

“Add ammonia since it dissolves each halide precipitate differently

Chloride dissolves very easily

Bromide dissolves in concentrated NH~3

Iodide isn’t soluble in NH~3”

89
Q

“What is the ionic equation for halide tests?

“

A

“Ag+ (aq) + X- (aq)
–>
AgX (s)”

90
Q

“How do you test for carbonates?

“

A

“Add acid to produce carbon dioxide

Bubble through limewater so the carbon dioxide turns the limewater cloudy”

91
Q

What do you need to know about sulfates to understand sulfate tests?

A

“All sulfates are soluble in water

Except for barium sulfate”

92
Q

“How do you test for sulfates?

“

A

“React compound with barium chloride or nitrate

BaSO~4 precipitate will form if compound is a sulfate”

93
Q

“What is the problem with sulfate tests?

What do you have to do because of this?”

A

“If the compound is a carbonate

The sulfate test result will be positive

This means that you have to do a carbonate test first to verify that it isn’t a carbonate

Then do the sulfate test”

94
Q

“If you are doing halide tests, what do you need to do in the sulfate test differently?

A

“Don’t use BaCl~2 because the chlorine will make the halide test positive automatically

95
Q

How do you test for NH~4 +?

A

“Add a hydroxide to produce ammonia gas

Ammonia gas is the only common alkaline gas

So use litmus paper which will turn blue if the ammonia is present
“

96
Q

What order do you have to do halide, carbonate, sulfate and ammonium tests?

A

“Carbonate then sulfate then halide

You can do ammonium test at any point
“

97
Q

How do group 2 elements react with oxygen?

A

“2X (s) + O~2 –> 2XO

Where X is a group 2 element”

98
Q

“Give the reaction for group 2 and water

A

“X (s) + 2H~2 O (l)
–>
X(OH)~2 (aq) + H~2 (g)

Where X is a group 2 element

99
Q

What happens when a group 2 oxide reacts with water?

A

“XO + H~2 O
–>
X 2+ + 2OH -

When solution becomes saturated, precipitate is produced:

X 2+ + 2OH -
–>
X(OH)~2”

100
Q

What is the contact process and what is the catalyst?

A

“2SO~2 + O~2 –> 2SO~3

With V~2 O~5 catalyst

101
Q

What is the catalyst for reacting zinc with an acid?

A

Cu 2+ catalyst

102
Q

What is the name and charge of C~2 O~4?

A

Ethanedioate with a 2- charge

103
Q

“What are the 2 half equations for the following reaction:

2Al + Fe~2 O~3 –> 2Fe + Al~2 O~3”

A

“Al –> Al 3+ + 3e-

Fe 3+ + 3e- –> Fe”

104
Q

“If you know that one of the reactants is MnO~4 - and one of the products is Mn 2+

Show how you work out the equation step by step”

A

“Firstly, you ALWAYS balance the oxygens by putting H~2 O’s on the other side:

MnO~4 - –> Mn 2+ + 4H~2 O

Now you balance the hydrogens by putting H+ on the other side

MnO~4 - + 8H+ –> Mn 2+ + 4H~2 O

You then count the oxidation numbers and put electrons in to balance the oxidation numbers:

MnO~4 - + 8H+ + 5e- –> Mn 2+ + 4H~2 O

”

A-Level Chemistry (25 decks)

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