Optical Isomerisation
Acids & Bases
Equilibria
Period 3 Chemistry
Random
100

What does a molecule need to show optical isomerisation?

Chiral Carbon

100

State the meaning of the term weak acid.

partially dissociates in water

100

2 features of a reaction in dynamic equilibrium

rate of forwards reaction = rate of backwards reaction

[Products] & [Reactants] remains constant

100

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

100

Test for Aldehydes + Results

Tollens Reagent

Silver Mirror

200

What's a racemic mixture?

50/50 split of enantiomers 

200

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-]

200

What is the only factor that affects Kc & Kp

Temperature

200

Give the formula of a hydroxide of an element in Period 3 used in medicine.

Mg(OH)2
200

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

300

Describe how you distinguish between separate samples of the two enantiomers

Use Plane polarised light

rotates (the plane of) in opposite directions

300

Give an expression for the acid dissociation constant for propanoic acid. (C2H5COOH)

[H+] [C2H5COO-] / [C2H5COOH]

300

Write the Kp equation for

2 SO2(g) + O2(g) ⇌ 2 SO3(g)

pp(SO3)2 / pp(SO2)pp(O2)

300

Phosphorus burns in air to form phosphorus(V) oxide. Give an equation for this reaction.

4P + 5O2 → P4O10

300

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

400

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)

400

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

400

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

400

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

400

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

500

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.

500

Calculate the pH of the solution formed after the addition of 35.0 cmof 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

500

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

500

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  

500

The organic product in part (a) can be converted into the alcohol shown. 

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FChemistry%2FA-level%2FTopic-Qs%2FAQA%2FOrganic-II%2F3.09-Carboxylic-Acids-and-Derivatives%2FSet-I%2FCarboxylic%2520Acids%2520and%2520Derivatives%2520QP.pdf

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