equations//reactions Flashcards
Metal + acid –>
Metal salt + H^2
Metal + water –>
Metal hydroxide + H^2
Metal carbonate + acid –>
Metal salt + carbon dioxide + water
How many moles are there in 12g of carbon-12?
n = m / Mr
= 12g / 12g/mol
= 1 mole
How many atoms are there in 2 moles of carbon-12?
No. of atoms = N~A * n
= (6.02 10^23) 2
= 1.204 * 10^24 atoms
If 2H~2 and CO~2 are products and hydrogen is useful, what is the atom economy?
“Mr of all = 48
Mr of 2H~2 = 4
Atom economy = (4 * 100%) / 48 = 8.33%
Atom economy is 8.33%”
The mass of CuSO~4.xH~2O = 6.8g and the mass of anhydrous CuSO~4 = 4.35g. Find x
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
What volume is taken up by 10 mol of CO~2?
“N = V / 24
V = 24N
V = 24 dm^3 mol^-1 * 10mol
V = 240 dm^3”
Find the volume of 64g of O~2 gas
“2 formulas are needed here
N = m / Mr = 64g / 32
2 moles of oxygen gas
V = 24N
V = 24 * 2
V = 48dm^3”
“SiCl~4 + 2H~2O
There is 5g of SiCl~4.
Find the mass of the 2H~2O”
“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”
What temperature gives a molar volume of 24dm^3 mol^-1?
“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”
Find the concentration of 0.0032 mol of HCl dissolved in 250cm^3
“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”
“Find the mass of KOH needed to prepare 250cm^3 of a 0.2mol dm^-3 solution
The Mr of KOH = 56.1”
“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”
“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”
“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”
“A solution contains 0.564g of CaCl~2 in 250 cm^3 of water
Find the mass concentration
“
“Mass concentration = 0.564g / 0.25dm^3
= 2.26 g dm^-3”
“A solution of NaOH has a concentration of 0.25 mol dm^-3
Calculate the mass concentration”
“Mass concentration = 0.25 * 38
= 9.5 g dm^-3”
How do the 4 main acids dissociate?
“H~2 SO~4 –> 2H+ + SO~4 2-
HCl –> H+ + Cl-
HNO~3 –> H+ + NO~3-
CH~3 COOH –> H+ + CH~3 COO-“
How many chlorine ions surround each sodium ion and how many sodiums surround each chlorine in sodium chloride?
“6 sodium around each chlorine
6 chlorine around each sodium”
How would you draw water in 3D?
“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”
What is the polarity of a C-H bond? You need to remember this
“Non-polar
Unusual as it seems”
What is the IMF for HCl?
“Permanent dipole-dipole forces
You have to remember this”
“Describe and explain how electrical conductivity in mercury bromide and in mercury in both solid and molten states
5 marks”
“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”
“There are 3 carbons in the chain
There is a chlorine on the first and second carbon
Name this organic”
“The base alkane is propane
So it is called:
1, 2 - dichloropropane”
“The base alkane is ethanol
If there are 3 bromines on one of the carbons
What is the name of this organic?”
1, 1, 1 - tribromoethane
If there are 4 halogens on an organic, what is the prefix used before the halogen name?
Tetra
E.g 1, 2, 3, 4 - tetrafluorobutane
“What are the 3 structural isomers of C~5 H~12?
Give their names and structural formulas”
“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”
What are the 5 structural isomers of C~6 H~14?
“Hexane
2-methylpentane
3-methylpentane
2, 2-dimethylbutane
2, 3-dimethylbutane”
What are the 2 structural isomers for C~3 H~7 Cl?
“1-chloropropane
2-chloropropane
“
What is the combustion equation for hexane?
“C~6 H~14 + 9.5O~2
–>
6CO~2 + 7H~2 O
What is the incomplete combustion of pentane?
“C~5 H~12 + 5.5O~2
–>
5CO + 6H~2 O
What is the complete combustion of propanol?
“C~3 H~8 O + 4.5O~2
–>
3CO~2 + 4H~2 O”
“What do you have to always remember in combustion of alcohols?
Don’t forget that there is always one oxygen on the LHS when you try to balance it
How is homolytic fission shown in an equation?
“H~3 C-CH~3
–>
H~3 C• + •CH~3
The 2 products are radicals”
“How do you write an equation for heterolytic fission?
“
"H~3 C-Cl --> H~3 C+ \+ Cl-"
Show the addition reaction of but-2-ene and water
“C~4 H~8 + H~2 O –> C~4 H~10 O
Butan-2-ol is formed”
What are the initiation, propagation and termination stages of CH~4 + Br~2?
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
Show how chlorine and ethane can react to form a molecule with 4 carbon atoms
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
Show how oxygen gas forms ozone
“O~2 –> 2O•
O~2 + O• O~3”
What is the general equation for how ozone is removed?
O~3 + O –> 2O~2
“Show how CFCs remove ozone
“
“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
Show how NO• removes ozone
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
What is the reaction from hexane to cyclohexane?
“C~6 H~14 –>
C~6 H~12 + H~2”
How do you draw the stereoisomers of 2-methylbut-2-ene?
“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”
How do you test for alkenes and cycloalkenes?
“Add bromine water
If it is an alkene or cycloalkene
The bromine water will turn from orange to colourless”
What is the reaction for bromine water added to alkenes?
“Example:
Ethene + Bromine –> 1,2-dibromoethane”
What is the reaction between cyclohexene and fluorine?
They make 1,2-difluorocyclohexane
“How is margarine made?
Hydrogenation of plant oils
“Which products are made with the reaction between but-1-ene and HCl?
Which one is favoured?”
“1-chlorobutane
2-chlorobutane
2-chlorobutane is favoured”
How do you draw the addition polymerisation of poly(propene)?
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
If the exam wants you draw “3 repeat units of poly(propene)”, what do you draw?
“Draw 3 repeat units in a chain bonded together
Draw brackets around this and show the bonds going through the brackets”
What are the reagents and conditions for electrophilic addition of alkenes?
“Steam
Acid catalyst”
What is the enthalpy change of the thermal decomposition of calcium carbonate?
+ 178 kJ mol^-1
“What is the standard formation equation of ammonia
“
"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”
“What is the density of water / a solution?
“
“1 g cm^-3
Remember that it is grams and centimetres”
Show the enthalpy change combustion reaction for ethane
“C~2 H~6 + 3.5O~2
–>
2CO~2 + 3H~2 O”
Describe the practical experiment for determination of enthalpy change of combustion
“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”
“Do alcohols dissolve in water?
Explain”
“They do dissolve in water
Because they are polar due to their hydrogen bonds”
“In the oxidation of alcohols
What is the oxidising agent?
“Acidified potassium dichromate
H+ | K~2 Cr~2 O~7
“How do you write the equation for the oxidation of an alcohol by distillation?
“
“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”
“What are the observations of all primary alcohol oxidation reactions?
“Acidified potassium dichromate goes from orange to green
“How do you write the equation for reflux oxidising alcohols?
“
“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”
What is the observation when oxidising secondary alcohols?
Still colour change from orange to green
How do you write the reaction for oxidation of secondary alcohols?
“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
Describe the dehydration of alcohols
“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
With dehydration of alcohols, what is different when secondary alcohols are used?
“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
What are the conditions and reagents of alcohol substitution? (Where an OH is replaced by a halogen)
“Reflux the alcohol
With sulphuric acid and sodium halide
(The halide contains the halogen that we want in the haloalkane)
Why is a sodium halide used in substitution of alcohols?
The hydrogen halide on its own doesn’t work for some reason
What is the first reaction which happens in substitution of alcohols?
“NaX + H~2 SO~4
–>
NaHSO~4 + HX
Where X is the halogen”
“What is the second reaction which happens in substitution of alcohols?
Use ethanol as the alcohol”
“C~2 H~6 O + HX
–>
C~2 H~5 X + H~2 0
Where X is the halogen”
“What is the overall reaction of alcohol substitution?
Use propanol as the alcohol and chlorine as the halogen”
“C~3 H~8 O + NaCl + H~2 SO~4
–>
C~3 H~7 Cl + NaHSO~4 + H~2 O”
“Why are the boiling points of branched alcohols less than boiling points of straight chain alcohols?
2 marks”
“Less points of contact between branched alcohols
So less energy required to break London forces in branched alcohols”
“What happens to do with dipoles in haloalkanes?
“
“The X gets a delta -
The C attached to it gets a delta +
Due to a significant electronegativity difference”
“What are the hydrolysis conditions and reagents?
“Hot aqueous sodium / potassium hydroxide
A reflux
“What is the overall reaction of hydrolysis?
For C~3 H~7 Cl as the haloalkane:
“C~3 H~7 Cl + OH-
–>
C~3 H~8 O + Cl-“
What are the reagents used to measure rate of hydrolysis of primary haloalkanes?
“Water
AgNO~3
Ethanol”
What is the ionic equation for silver and halide ions in rate of hydrolysis?
Ag+ + X- –> AgX
What is the overall rate hydrolysis equation?
“Haloalkane + water + AgNO~3
–>
Alcohol (from haloalkane) + HNO~3 + AgX
AgX is the precipitate formed “
“What is the difference between the rate of hydrolysis of a flouroalkane compared to a iodoalkane and why?
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
“Give the 5 steps of mass spectrometry
“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”
“List all the Quickfit apparatus needed in reflux
5 items needed”
“Pear-shaped flask
Receiver
Screw-tap adaptor
Condenser
Still head”
What are the actual values for the temperature and pressure of the Haber process?
“350 - 500 C temperature
100 - 200 atm (atmospheres) pressure”
What percentage of reactants in the Haber process are turned into ammonia?
Only 15% of reactants
What is the chemical equation showing lithium being ionised?
“Li(g) –> Li(g)+ + e-
The gas state symbols are very important”
What is the reaction for the redox displacement of chlorine and bromide?
“Cl~2 + 2Br-
–>
2Cl- + Br~2”
What are the colours of the different halogens in both water and cyclohexane?
“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
“How do you do halide tests?
(Different to redox displacement)”
“Dissolve halide in water
Add aqueous silver nitrate
Silver halide precipitate is formed and its colour tells us what the halide is”
“In halide tests
What are the precipitate colours for the different halides?”
“Chloride gives white
Bromide gives cream
Iodide gives yellow”
“How do you confirm the halide test result?
“
“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”
“What is the ionic equation for halide tests?
“
“Ag+ (aq) + X- (aq)
–>
AgX (s)”
“How do you test for carbonates?
“
“Add acid to produce carbon dioxide
Bubble through limewater so the carbon dioxide turns the limewater cloudy”
What do you need to know about sulfates to understand sulfate tests?
“All sulfates are soluble in water
Except for barium sulfate”
“How do you test for sulfates?
“
“React compound with barium chloride or nitrate
BaSO~4 precipitate will form if compound is a sulfate”
“What is the problem with sulfate tests?
What do you have to do because of this?”
“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”
“If you are doing halide tests, what do you need to do in the sulfate test differently?
“Don’t use BaCl~2 because the chlorine will make the halide test positive automatically
How do you test for NH~4 +?
“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
“
What order do you have to do halide, carbonate, sulfate and ammonium tests?
“Carbonate then sulfate then halide
You can do ammonium test at any point
“
How do group 2 elements react with oxygen?
“2X (s) + O~2 –> 2XO
Where X is a group 2 element”
“Give the reaction for group 2 and water
“X (s) + 2H~2 O (l)
–>
X(OH)~2 (aq) + H~2 (g)
Where X is a group 2 element
What happens when a group 2 oxide reacts with water?
“XO + H~2 O
–>
X 2+ + 2OH -
When solution becomes saturated, precipitate is produced:
X 2+ + 2OH -
–>
X(OH)~2”
What is the contact process and what is the catalyst?
“2SO~2 + O~2 –> 2SO~3
With V~2 O~5 catalyst
What is the catalyst for reacting zinc with an acid?
Cu 2+ catalyst
What is the name and charge of C~2 O~4?
Ethanedioate with a 2- charge
“What are the 2 half equations for the following reaction:
2Al + Fe~2 O~3 –> 2Fe + Al~2 O~3”
“Al –> Al 3+ + 3e-
Fe 3+ + 3e- –> Fe”
“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”
“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
”
