moduel 5

Definition of atomisation

is the enthalpy change due to the formation of 1 mole of an ionic lattice from gaseous ions.

The enthalpy changes of solution of the magnesium halide show a trend form MgF2 to MgI2

Explain why it is difficult to predict wether the enthalpy changes of solution becomes more exothermic or less exothermic n down the group form MgF2 to MGI2

• MgF2 and MgI2 are both getting less exothermic because the ions are becoming larger

• So lattice enthalpy and hydration enthalpy are getting getting less exothermic

• So difficult to predict wether lattice enthalpy or hydration enthalpy has a bigger effect

Standard enthalpy change of formation

enthalpy change due to 1 mole of a compound forming from its constituent elements under standard conditions

Standard enthalpy change of atomisation

enthalpy change of forming of 1 mole of gaseous atoms from the element in its standard state under standard conditions. • This is always endothermic (as it is bond breaking).

First ionisation energy And if it’s needs or exothermic

is the enthalpy change

required to remove one electron from each atom in 1 mole of gaseous atoms to form one mole of +1 gaseous ions. • Always endothermic (as energy need to overcome nuclear

attraction).

First electron affinity and weather its eno or exhothermic

is the enthalpy change

when an electron is added to each atom in 1 mole of gaseous atoms to form one mole of –1 gaseous ions. • Always exothermic (as electron attracted towards nucleus).

Why is the second electron affinity endothermic

Second EA is endothermic as electron is repelled by negative

ion.

What is the measurement of ionic bonds

lattice enthalpy

Why is lattice enthalpy always exothermic

Energy is given out when gaseous ions attract to form a lattice.

What does A more exothermic lattice enthalpy value mean

A more exothermic lattice enthalpy value means higher melting and boiling points as more energy is required to overcome the electrostatic interactions.

When do the most exothermic lattice enthalpies arise

When ions are small, because the ions can get closer

When ions have larger charges, as these ions have stronger

electrostatic forces

Standard enthalpy change of hydration

Accompanies one mole of gaseous ions dissolving in water under standard conditions

Explain the trends of sodium halides down the group

• as ionic radius increases

• Attraction between ions decreases

• Less energy released on formation

• Lattice enthalpy is less negative

Enathalpy change of solution

The enthalpy change accompanying one mole of solute dissolving in water under standard conditions

Why are hydration enthalpies always exothermic

Becuase you are forming new bonds between gaseous ions and water molecules

Why is enthalpy change of solution endo or exothermic

• because the lattice breaks to form gaseous ions

• Then the gaseous ions are attracted the the polar water molecules so a bond is formed

List possible sources of in an enthalpy change experiment and explain how they could be reduced

• If not all the solid is transferred from the weighing boat -

  weighing the weighing boat after the solid has been added.

• Thermometer has accuracy of +0.5 °C which is significant for

  such small temperature changes - Use a datalogger and a

  temperature probe or a more accurate thermometer (0.1°C).

• It is difficult to see if the solid has dissolved

• Measuring cylinder has accuracy of +1cm3 which is 3.8% for

  50cm3 - Use a more accurate measuring cylinder

Devein a redox reaction

Rreaction involving reduction and oxidation

Reduction reaction

Decrease in oxidation number or a gain of electrons

Define oxidation

An increase in oxidation number or a loss in electrons

What is a reducing agent

An electron donor

Oxidising agent

An electron acceptor (gets reduced in the process)

What is a half equation

Either the reduction process or the oxidation process

What is an electrochemical cell

• is a device that produces an electronmotive (e.m.f) as a result of a chemical reaction

• Each cell is made up from two half cells

• In one half cell the oxidation reaction takes place and reduction happens in the ohter

• A cell converts chemical energy to electrical energy as ele thorns flow between the half cells lined by external circuit

Electrochemical circuits: what are the two half cells connected by

• a circuit containing a voltmeter

• A salt bridge

Electrode potentials - what does the flow of direction depend on

The tendency on each electrode to release electrons

What does the voltmeter measure (electrode potentials)

• the energy released by the transfer of electrons between half cells

What is the measured voltage called

• the electrode potential

What is the electrode potential

Is the difference between the standard electrode potentials of each half cell

What is the standard electrode potentials of each cell compared to

Standard Hydrogen cell

How can we determine the electrode potential

• by connecting it to a hydrogen feul cell

• The tendency for different cells to accept or release electrons is measured as the electronmotive force (measured in volts)

What is the electrochemical series

• the order of the standard electrode potentials of the cells

What does a more negative electrochemical value mean

• the more readily it will give up electrons ( undergo oxidation)

What does a more positive electrochemical value mean

• the greater the tendency for reduction (the more readily it will gain electrons)

Define term standard electrode potential

The e.m.f (electromotive force) of a half cell compared to a standard hydrogen half cell at 1 mol dm-3, 100kPa and 298K

What is a ligand

Is a molecule or ion that donates a pair of electrons to a central metal ion to form a dative covalent bond

What is a ligand substitution reaction

Where one ligand in a complex ion is replaced by another ligand

What is a the definition of a bindentate ligand

• donates two electron pairs to a metal ion

• And forms tow dative bonds to a metal ion

What is the definition of a transition metal

A d- block element that has an ion with an incomplete d sub shell

Out of the 4s and 3d sub shells which shell is filled first and which shell loses electrons first

• The 4s sub-shell is filled first

• The 4s electrons are lost first

Explain the use of two deuterated compounds in NMR spectroscopy

• CDCl3 used as a solvent

• D2O used to identify OH or NH protons

Protperties of transition elements that mKE THEM different form ohter metals

• they form compounds in which the transition elements has different oxidation states

• They form coloured compounds

• The elements and their compounds can be used as catalysts

What transition metal is used as a catalyst in the harbour cycle

Iron

What catalyst is used in the contact process

Vanadium oxide (2SO2 + O2 — 2SO3)

What catalyst is used in hydrogenation

Nickel

What catalyst is used in the decomposition of hydrogen peroxide to oxygen and magnese(IV) oxide

MnO2

What is a ligand

A molecule or ion that donate a pair of electrons to a central metal ion to form a coordinate bond or dative covalent bond

What reaction does Fe2+ catalyse

S2O8 2- (aq) + 2I- (aq) — 2SO4 2- (aq) + I2 (aq)

Adding Fe2+ forms the blue - black iodine solution much more quickly

Diefintion of a bidentete ligand

Can donate two lone pairs of electrons to the central metal ion, forming tow dative bonds

What complex ion can be used in cancer drugs and how does it work

• cis - platin (Pt(NH3)2(Cl)2)

• Forms a platinum complex inside of a cell whihc binds to DNA and prevents the DNA of the cell form replicating. Activation of the cells own repair mechanisms led to apoptosis

How is ligand substitution important in haemaglobin

• the central metal ion is Fe2+ and can bind to oxygen gas

• This forms oxyheamaglobin and can be carried around the body to be used in respiration

What is a precipitation reaction

When two aqueous solutions contains ions react to form and insoluble ionic compound solid called a precipitate