PAGs and High mark Q Flashcards
Magnesium nitrate is used in fertilisers as a source of nitrogen.
* A student plans to prepare 250.0 cm3 of a 0.4000 mol dm–3 solution of magnesium nitrate,
starting from magnesium nitrate crystals, Mg(NO3)2*6H2O.
Describe how the student would prepare the solution, giving full details of quantities, apparatus
and method.
.weigh mass of crystals to 2 decimal places
.dissolve in distilled water
.transfer to 250 cm3 volumetric flask
.rinse beaker and transfer washing to flas
.make up to the mark with water till the bottom of menisucs is on the mark
.calculate mass- find moles then times moles by mr
This question is about magnesium, bromine and magnesium bromide.
Table 16.1 shows some physical properties of magnesium, bromine and magnesium bromide
Explain the physical properties shown in Table 16.1 using your knowledge of structure and
bonding.
Magnesium:
.gaint lattice, metallic bonding and has delocalised electrons
Bromine:
.simple molecular, london forces between molecules
magnesium bromide:
.gaint lattice, ionic bonding between oppo charged ions
.metallic and ionic bonds are stronger then london
The reaction of barium with bromine is more vigorous than the reaction of calcium with
bromine.
.Ba has a greater atomic radius then Ca
.nuclear attraction is less in Ba
.Ionisation energy of Ba is less
B and C are ionic compounds of two different Group 1 elements.
The molar masses of B and C are both approximately 140 g mol−1.
A student dissolves B and C in water in separate test tubes and analyses the solutions.
The observations are shown below
Use this information and the observations to identify the formulae of B and C.
Explain your reasoning.
.carbonate gas is released in B
.sulfate precipitate is formed in C
.140 - MM of CO3
.140 - MM of SO4
.B = K2CO3
.C = Na2SO4
1-Bromobutane is an organic liquid with a boiling point of 102 °C.
A student prepares 1-bromobutane by reacting butan-1-ol with sulfuric acid and sodium bromide.
The student boils the mixture for one hour.
The equation is shown below.
CH3CH2CH2CH2OH + H+ + Br− → CH3CH2CH2CH2Br + H2O
The student obtains a reaction mixture containing an organic layer (density = 1.27 g cm−3) and an
aqueous layer (density = 1.00 g cm−3).
i. * Draw a labelled diagram to show how you would safely set up apparatus for the
preparation. Outline a method to obtain a pure sample of 1-bromobutane from the
reaction mixture.
.draw round bottom flask
.with heating mantle
.condenser on top of flask
.use separating funnel to separate organic and aqueous layers
.dry with anhydrous salt like MgSO4
.Redistillation collect fraction distilling at 102C
Alcohols can be converted into alkenes in an elimination reaction.
The elimination of H2O from pentan-2-ol forms a mixture of organic products.
Give the names and structures of all the organic products in the mixture.
Your answer should explain how the reaction leads to the different isomers.
.elimination can produce a double bond in 1- or 2- postion
.this leads to the formation of structual isomers
.pent-2-ene has sterioisomerism due to their being two diff groups on each carbon
.draw pent-1-ene, Z pent-2-ene and E pent-2-ene
Describe the oxidation reactions of butan-1-ol forming an aldehyde and a carboxylic acid.
Explain, using a diagram, how the aldehyde can be produced in the laboratory by controlling the
reaction conditions.
,draw heart shape flask with tube going up and to the right connected to condenser leading to flask
aldehyde:
.use acid and dichromate
.heat and distillation
.butanal is formed
.CH3CH2CH2CH2OH + [O] -> CH3CH2CH2CHO + H2O
carboxylic acid:
.acid and dichromate
.heat under reflux
. butanoic acid is formed
.CH3CH2CH2CH2OH + 2[O] →
CH3CH2CH2COOH + H2O
The branched-chain alcohol J, C5H12O, was heated under reflux with excess H2SO4 / K2Cr2O7 to
form an organic compound K with the infrared spectrum below.
Determine the structures for the branched-chain alcohol J and compound K.
Your answer should explain all your reasoning using the evidence given.
* Write an equation for the reaction of J when heated under reflux with excess H2SO4 /
K2Cr2O7 to form K.
Use [O] to represent the oxidising agent
.Evidence of the IR absorption at 1720 for presence of carbonyl group
.no peak between 2500–3300 cm−1
.so J is a secondary alcohol
.draw secondary alcohol
.draw secondary alcohol as ketone
.C5H12O + [O] → C5H10O + H2O
Compound B, CxHyO, can be oxidised to form a ketone C.
0.035 mol of B has a mass of 2.59 g.
Compound B reacts with compound D, C3H6O2, in the presence of an acid catalyst to form two
compounds E and F.
* Calculate the molar mass of compound B.
* Give the structures of compounds B, C, D, E and F.
.calculate MM of B by timing mol by mass
.B =draw C4H10O with OH on 3rd C
.C = draw ketone of C4H10O
.D = draw ketone with OH group on the bottom
.EandF = look at phone
.water
Describe the oxidation reactions of propan-1-ol when using a suitable oxidising agent.
Indicate how the use of different reaction conditions can control which organic product forms.
Include reagents, observations and equations in your answer.
In your equations, use structural formulae and use [O] to represent the oxidising agent.
.regents- H+ and Cr2O7^2-
.colour change from orange to green
.distillation produces CH3CH2CHO
.CH3CH2CH2OH + [O] → CH3CH2CHO + H2O
.reflux produces CH3CH2COOH
.CH3CH2CH2OH + 2[O] → CH3CH2COOH + H2O
A student carries out the reaction in Equation 16.1 using 9.26 g of alcohol A.
The student obtains a liquid reaction mixture containing a mixture of organic products
and the acid catalyst.
The student purifies the reaction mixture to obtain the liquid alkene B with a percentage
yield of 75.0%.
Describe a method to obtain a pure, dry sample of alkene B from the reaction mixture
and calculate the mass of alkene B that the student produced.
.Use a separating funnel to separate organic and aqueous layers
.dry with anhydrous salt like MgSO4
.redisillation
.mass of B = find mole of A then do mole of A times 75/100
.times that number by 84
You are provided with three alcohols that are structural isomers: CH3CH2CH2CH2OH,
CH3CH2CHOHCH3 and (CH3)3COH. You do not know which is which.
You have access to normal laboratory apparatus and chemicals, Quickfit apparatus, and an
infrared spectrometer.
Describe a plan that would allow you to identify the three alcohols using the same experimental
set up and method.
You should provide
* equations using structural formulae for any reactions
* a description of how you will identify the three alcohols from any observations and
results.
.use H+ and Cr2O7^2- and reflux
.CH3CH2CHOHCH3 + [o] →
CH3CH2COCH3 + H20
.CH3CH2CH2CH2OH + 2[o] →
CH3CH2CH2COOH + H2o
.IR: carboxylic acid from broad OH absorption and C=O
IR: carbonyl / ketone from C=O and no OH
.tertiary alcohol from no colour change
A student carries out test-tube experiments to prove the trend in reactivity of halogens.
The student is provided with the following solutions:
* bromine water
* aqueous iodine
* aqueous barium chloride
* aqueous magnesium bromide
* aqueous calcium iodide.
Chlorine gas and chlorine water are not available.
The student carries out the minimum number of test-tube experiments using these solutions in
the presence of cyclohexane (an organic solvent).
* State the solutions that need to be added together in order to prove the trend in reactivity
of the halogens, using the minimum number of test-tube experiments.
* Describe the colour seen in the organic solvent at the end of each test-tube experiment.
* Write an ionic equation for one reaction that takes place.
.add barium chloride to bromine colour is yellow
.add calcium iodide to bromine colour is lilac
.add magnesium bromide to iodine
.Br2 + 2I -> I2 + 2Br-
This question is about nickel and its compounds.
A student is provided with samples of three nickel compounds.
One sample is nickel(II) bromide, another is nickel(II) sulfate and the third is nickel(II) carbonate.
The student doesn’t know which sample is which.
Describe the tests that the student could carry out to identify the anion (negative ion) in each
sample, and write equations for any reactions.
.carbonate test- add HCl = fizzing
.2HCl + NiCO3 → NiCl2 + H2O + CO2
.sulfate test- add BaCl2 = white precipitate is formed
.BaCl2 + NiSO4 → BaSO4 + NiCl2
.bromide test- add AgNO3 = cream precipitate is formed
.Ag+ + Br– → AgBr
You are supplied with a sample of ammonium bromide.
Describe simple tests that would identify the cation and anion present in ammonium bromide.
Include reagents, expected observations and relevant equations
test for Br-:
.use silver nitrate and observe cream precipitate
.Ag+ + Br- -> AgBr
test of NH4:
.heat with hydroxide and indicator turns blue
.NH4+ + OH- -> NH3 + H2O
