Optical Isomerisation
What does a molecule need to show optical isomerisation?
Chiral Carbon
State the meaning of the term weak acid.
partially dissociates in water
2 features of a reaction in dynamic equilibrium
rate of forwards reaction = rate of backwards reaction
[Products] & [Reactants] remains constant
Identify the element in Period 3, from sodium to chlorine, that has the largest atomic radius.
Na Mg Al Si P S Cl Ar
Na
Test for Aldehydes + Results
Tollens Reagent
Silver Mirror
What's a racemic mixture?
50/50 split of enantiomers
For pure water at 40 °C, pH = 6.67
A student thought that the water was acidic. Explain why the student was incorrect.
[H+] = [OH-]
What is the only factor that affects Kc & Kp
Temperature
Give the formula of a hydroxide of an element in Period 3 used in medicine.
Chlorine reacts with water to form a solution containing 2 acids.
Give the equation & why it is a redox reaction
Cl2 + H2O -> HClO + HCl
Cl oxidation state 0 -> +1 & -1
loses & gains electrons
Describe how you distinguish between separate samples of the two enantiomers
Use Plane polarised light
rotates (the plane of) in opposite directions
Give an expression for the acid dissociation constant for propanoic acid. (C2H5COOH)
[H+] [C2H5COO-] / [C2H5COOH]
Write the Kp equation for
2 SO2(g) + O2(g) ⇌ 2 SO3(g)
pp(SO3)2 / pp(SO2)2 pp(O2)
Phosphorus burns in air to form phosphorus(V) oxide. Give an equation for this reaction.
4P + 5O2 → P4O10
How the relative abundance of an ion is determined in a TOF mass spectrometer
at the detector plate the ions gain an electron
(relative) abundance depends on the size of the current
Explain why a reaction produces a racemic mixture.
planar carbonyl group
Attack from either side
With equal probability OR produces equal amounts (of the two isomers/enantiomers)
Which is the concentration of NaOH(aq), in mol dm–3 , that has pH = 14.30?
Kw = 1.00 × 10–14 mol2 dm–6 at 25 °C
2.00
2 SO2(g) + O2(g) ⇌ 2 SO3(g)
State and explain the effect, if any, of a decrease in overall pressure on the equilibrium yield of SO3
decreases yield
So equilibrium shifts to side with more moles/molecules or more moles/molecules on LHS
So equilibrium shifts (to left side) to oppose decrease in pressure OR to increase pressure
Explain why the atomic radii of the elements decrease across Period 3 from sodium to chlorine.
The number of protons increases (across the period) / nuclear charge increases
Therefore, the attraction between the nucleus and electrons increases
Definition of Lattice enthalpy of formation for NaCl
the enthalpy change that occurs when 1 mole of an ionic solid is formed from its constituent, gaseous ions
Butan-2-ol reacts with concentrated sulfuric acid to produce three isomeric alkenes. Name and outline a mechanism to show how any one of the alkenes is formed. Explain how this reaction can lead to the formation of each of these three alkenes.
Calculate the pH of the solution formed after the addition of 35.0 cm3 of 0.150 mol dm−3 NaOH to the original 25.0 cm3 of monoprotic acid.
The ionic product of water Kw = 1.00 × 10−14 mol2 dm−6 at 298 K.
Give your answer to two decimal places.
12.80
CH4(g) + H2O(g) ⇌ CO(g) + 3 H2(g) ΔH = +206 kJ mol−1
The reaction is done at a temperature of 800 °C and a low pressure of 300 kPa in the presence of a nickel catalyst.
Explain, in terms of equilibrium yield and cost, why these conditions are used.
Temperature
The reaction is endothermic (so equilibrium shifts to RHS to reduce the temperature)
So, higher temperature increases the yield
High temperatures are costly (so compromise temperature used)
Pressure
More moles of gas on the right hand side, (so equilibrium shifts to RHS to increase the yield)
So, lower pressure increases the yield
A low pressure means a low cost
Catalyst
Catalyst has no effect on yield
Adding a catalyst allows a lower temperature to be used
So, this lowers the cost
Explain, in terms of crystal structure and bonding, why silicon(IV) oxide has a higher melting point than phosphorus(V) oxide. (4)
SiO2 is macromolecular / giant covalent / giant molecule
Strong covalent bonds (between atoms) or covalent bonds need a lot of energy to be broken/overcome
P4O10 is molecular or simple covalent molecule
Weak van der Waals forces between molecules or van der Waals forces between molecules break easily
The organic product in part (a) can be converted into the alcohol shown.
Give the IUPAC name of the alcohol.
Give the reagent needed for this reaction and name the mechanism.
1-phenylpropan-1-ol
NaBH4 / LiAlH4
Nucleophilic addition