Past Paper 2020: 1,2,3 Flashcards
State why there is a difference between the theoretical and experimental value
Has covalent character or partial covalent bonding as well as ionic bonding
Explain why the Enthalpy of hydration becomes less exothermic from Li+ to K+
Size of ion increases, charge density decreases, electrostatic attraction between the metal ion and Od- of water decreases
Give the meaning of the term relative atomic mass
Average mass of an atom of an element/ 1/12 the mass of one atom of carbon 12
Give two reasons why it is necessary to ionise the isotopes of chromium before they can be analysed in the TOF spectrum
- So they will be accelerated by an electric field towards the negative plate
- So they can generate a current when hitting the detector
Explain why the atomic radius decreases across period 3 from sodium to chlorine
Same shielding, the number of protons increases
Identify the element in P3 that has the highest electronegativity
Chlorine
Phosphorous burns in air to give phosphorous oxide. Give an equation for this reaction
P4 + 5O2 —> P4O10
State the meaning of the term weak acid
Partially dissociates in water to form H+ ions
Some reactions of the [Al(H2O)6]3+ are shown
Colourless solution. <————————— [Al(H2O)6]3+ —————> B white precipitate
Containing complex ion A. Na4EDTA I. NaOH. Na2CO3
I
White ppt that reacts to form a colourless solution containing complex ion C
Give the formula of the white ppt B
State one other observation when Na2CO3 is added to a solution containing the 3+ ion, give an equation for this reaction
Give the formula of C and write an equation
Formula of complex ion a
B:
[Al(H2O)3(OH)3]
[Al(H2O)6]3+ + 3CO32- —> 2[Al(H2O)3(OH)3] + 3CO2 + 3H2O
Producing effervescence
C:
[Al(H2O)2(OH)4]-
Excess NaOH
[Al(H2O)3(OH)3] + 4OH- —> [Al(H2O)2(OH)4]- + 4H2O
A: [Al9EDTA)]-
Explain with the use of an equation why a solution containing [Al(H2O)6]3+ has a pH <7
[Al(H2O)6]3+ + H2O = [Al(H2O)5(OH)]2+ + H3O+
Al3+ has a small size and a higher charge density- weakens O-H bond, releasing H+
State the effect of the addition of a catalyst on the value of Kp
Increase- catalyst does not effect the position of the equilibrium
Explain why the melting points of these two compounds are different- XeF4 and PF3 by referencing their shapes
XeF4 has 4Bonding pairs and 2 lone pairs around xe
PF3 has 3 bonding pairs and 1 lone pair around P
XeF4 is square planar
PF3 is pyramidal
Electron pairs repel as far as possible
The relative strength of the intermolecular forces in XeF4, XeF4 has vander waal forces and PF3 has dipole dipole forces. Stronger intermolecular forces in XeF4 due to larger Mr or more electrons or larger molecules or packs more closely together.
State when is observed when silver nitrate solution is added to sodium fluoride
No precipitate formed
State what is observed when silver nitrate solution is added to sodium fluoride solution
White fumes
NACl + H2SO4 —> NaHSO4 + HCl
Acts as a base
Give an equation for the redox reaction between solid sodium bromide and concentrated sulfuric acid
Explain using oxidation states, why this is a redox reaction
2NaBr + 2H2SO4 —> Na2SO4 + Br2 + SO2 + 2H2O
Br changes from -1 to O so it becomes oxidised
S changes state from +6-+4 so is reduced
State what is observed when aqueous chlorine is added to sodium bromide solution
Give an ionic equation for the reaction
Brown/orange solution
Cl2 + 2Br- —> 2Cl- + Br2
Define the term overall order of reaction
The sum of powers/indices to which concentrations are raised in the rate equation
Suggest a simple way to detect if Ethanolic acid has reacted
Producers a sweet smell
Describe how infrared spectra can be used to distinguish between isomers
Each isomer will have a unique fingerprint region below 1500- compare to a known date base
Suggest two ways in which the melting point of the crude aspirin collected would differ from the melting point of pure aspirin
Value will be lower
Range of values will be differnt
Describe two important precautions when heating the mixture of ethanol and crude aspirin
Ethanol is flammable so use water bath to heat
Heat temperature to below boiling point so ethanol does not boil away
A small amount of cold ethanol is then poured through the Büchner funnel
Explain the purpose of this
To remove any soluble impurities
Describe one difference you would expect to see between crude and purified aspirin
Pure product will have larger crystals and will be shinier
Define the term electronegativity
Explain the polarity of the C-Br bond in 2-bromopropane
The relative ability of an atom to attract a pair of electrons in a covalent bond
Br is more electronegative than C
So Br is d- and C is d+
When an excess of water is added to ethanol a similar Nucleophilic addition reaction occurs. Suggest why this reaction is slower that the reaction in part with chloroethanl
C in C=O is less d+ because CH3 attached is donating an electron so there is a higher activation energy
