question

Standard enthalpy of formation

answer

The enthalpy change when one mole of a compound is formed from its elements under standard conditions, with all substances in their standard states.

question

Standard change of atomisation

answer

The enthalpy change when one mole of gaseous atoms is formed from the element in its standard state under standard conditions.

question

First ionisation energy

answer

The enthalpy change needed to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions.

question

Second ionisation energy

answer

The enthalpy change required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions.

question

First electron affinity

answer

The enthalpy change when one electron is added to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions.

question

Second electron affinity

answer

The enthalpy change when one electron is added to each ion in one mole of gaseous 1- ions to form one mole of gaseous 2- ions.

question

Lattice enthalpy

answer

The enthalpy change that accompanies the formation of one mole of a solid compound from its gaseous ions under standard conditions.

question

The standard enthalpy change of solution

answer

The enthalpy change when one mole of a compound is completely dissolved in water under standard conditions.

question

The standard enthalpy change of hydration

answer

The enthalpy change that accompanies the dissolving of gaseous ions in water to form one mole of aqueous ions.

question

Entropy

answer

A measure of the dispersal of energy in a system, which is greater the more disordered a system.

question

ΔS=

answer

S of products - S of reactants

question

Effect of increasing ionic size on lattice enthalpy

answer

This leads to a weaker attraction between oppositely charged ions so there is a less exothermic lattice enthalpy.

question

Effect of increasing ionic charge on lattice enthalpy

answer

This leads to a stronger attraction between oppositely charged ions and a more exothermic lattice enthalpy.

question

Effect of increasing ionic size on hydration enthalpy

answer

This leads to a weaker attraction between the ions and water molecules so there is a less exothermic hydration enthalpy.

question

Effect of increasing ionic charge on hydration enthalpy

answer

This leads to a stronger attraction between ions and water molecules so there is a more exothermic hydration enthalpy.

question

ΔG=

answer

ΔH-TΔS

question

A process can take place spontaneously (i.e. is feasible), when...

answer

ΔG<0

question

Free energy change

answer

The overall change in energy during a reaction.

question

A reaction is feasible at any temperature if...

answer

The sign of its ΔH is negative and its ΔS is positive, because ΔG will always be less than zero.

question

A reaction is NOT feasible at any temperature if...

answer

The sign of its ΔH is positive and its ΔS is negative, because ΔG will always be more than zero.

question

A reaction is only feasible at high temperatures if...

answer

The sign of its ΔH is positive and its ΔS is positive as increasing the temperature will increase the magnitude of TΔS, until the magnitude of TΔS becomes greater than the magnitude of ΔH, so ΔG will become less than zero and the reaction will become feasible.

question

A reaction is only feasible at low temperatures if...

answer

The sign of its ΔH is negative and its ΔS is negative as decreasing the temperature will decrease the magnitude of TΔS, until the magnitude of TΔS becomes less than the magnitude of ΔH, so ΔG will become less than zero and the reaction will become feasible.

question

Why do reactions with ΔG<0 sometimes not take place?

answer

The rate of reaction is too slow or the activation energy is too high.

question

Proton relative mass and charge

answer

1 and 1+

question

Neutron relative mass and charge

answer

1 and 0

question

Electron relative mass and charge

answer

1/1836 and 1-

question

Mass number=

answer

Number of protons + number of neutrons

question

Atomic number=

answer

Number of protons

question

Isotopes

answer

Atoms of the same element (with the same number of protons) but with different numbers of neutrons and different masses.

question

Relative isotopic mass

answer

The mass of an isotope compared with one twelfth of the mass of an atom of carbon-12.

question

Relative atomic mass

answer

The weighted mean mass of an atom compared with one twelfth of the mass of an atom of carbon-12.

question

Relative molecular mass

answer

The weighted mean mass of a molecule compared with one twelfth of the mass of an atom of carbon-12.

question

Water of crystallisation

answer

The water present in hydrated salts.

question

To determine relative atomic mass...

answer

Multiply the isotopic mass by percentage abundance for each isotope then sum the results.

question

Avagadro's number

answer

The number of atoms in one mole of the substance. 6.02x1023

question

Mole

answer

The mass of substance containing the same number of atoms as there are in 12g of carbon-12.

question

Empirical formula

answer

The simplest whole-number ratio of atoms in a compound.

question

Atom economy=

answer

(Molar mass of desired product/Molecular mass of all products) x100

question

Hydrated salts

answer

Contain some water as part of their structure.

question

Anhydrous salts

answer

Hydrated salts after being heated so the water has been lost.

question

Molar volume

answer

The volume occupied by one mole of a substance at a given temperature and pressure.

question

Number of moles of gas at room temperature and pressure=

answer

V(dm3)/24

question

Ideal gas equation

answer

PV=nRT P is in pascals V is in m3 n is in mol T is in Kelvin

question

Concentration of a solution

answer

The amount of solute per dm3.

question

Standard solution

answer

A solution of a known concentration.

question

Concentration=

answer

n/V

question

Stoichiometry

answer

The relationship between relative quantities of substances taking part in a reaction.

question

Limiting reagent

answer

The reactant that is first to be used up so stops the reaction.

question

Apparatus uncertainty=

answer

(Number of readings x instrumental error/reading) x 100

question

Base

answer

A proton acceptor.

question

Acid

answer

A proton donor.

question

Strong acid

answer

An acid that completely dissociates in aqueous solution.

question

Weak acid

answer

An acid that partially dissociates in aqueous solution.

question

Neutralisation equation

answer

H+(aq) + OH-(aq) --> H2O(l)

question

Acid + base -->

answer

Salt + Water

question

Acid + carbonate -->

answer

Salt + water +carbon dioxide

question

Acid + alkali -->

answer

Salt + water

question

Method of preparation of a standard solution

answer

1. Weight the solid accurately. 2. Dissolve the solid in a beaker. 3. Transfer solution to a volumetric flask. Rinse traces of solution from the beaker into the flask. 4. Carefully fill the volumetric flask to the graduation line (read the meniscus at the bottom). 5. Invert the flask several times to ensure the solution is well mixed.

question

Method of an acid-base titration

answer

1. Using a pipette, we measure a volume of solution into a conical flask. 2. The other solution solution is placed in a burette and the volume recorded. 3. A few drops of indicator are added to the solution in the conical flask. 4. The solution in the burette is then added to the solution in the conical flask until the reaction has just completed. This is called the end point and is when we see a permanent change in colour. The volume in the burette is then recorded. 5. The volume of solution from the burette is then calculated and this is known as the titre. 6. The experiment is repeated until two titres are concordant to 0.10cm3 of each other. 7. The mean titre is then calculated (to 1 d.p.). Only concordant titres are used in the mean.

question

Atomic orbital

answer

A region within an atom that can hold up to 2 electrons, with opposite spins.

question

The 4s sub-shell fills before...

answer

The 3D sub-shell.

question

Ionic bonding

answer

The electrostatic attraction between oppositely charged ions.

question

Why do ionic compounds have high melting and boiling points?

answer

Lots of energy is required to break the strong electrostatic forces between oppositely charged ions.

question

Explain why molten or dissolved ionic compounds are able to conduct electricity.

answer

The ions are free to move throughout the substance and carry the charge.

question

Ionic lattices dissolve in...

answer

Polar solvents, such as water.

question

Why are some ionic substances less soluble than others?

answer

If a compound has very big ions then not many water molecules can fit round them. Also, strong charges are difficult to overcome so 3+ or 3- ionic compounds do not dissolve very well.

question

Metallic bonding

answer

The strong electrostatic attraction between positive Mel=tal ions and delocalised electrons.

question

Delocalised electrons

answer

Electrons that are not associated with a particular atom and are free to move throughout the structure.

question

Why do metallic compounds have high melting and boiling points?

answer

The strong electrostatic forces between positive metal ions and delocalised electrons need a lot of energy to be overcome.

question

Why are metallic compounds able to conduct electricity as solids and liquids?

answer

The delocalised electrons are free to move throughout the structure and can pass on the electrical current.

question

Why do metallic compounds have poor solubility?

answer

The electrostatic attraction is too strong to be broken by polar solvents surrounding each ion in solution.

question

Covalent bonding

answer

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

question

Lone pair

answer

An outer shell pair of electrons that are not involved in chemical bonding.

question

Dative (co-ordinate) covalent bonds

answer

This is when one of the atoms supplies both of the electrons that form the bond.

question

Bond enthalpy

answer

A measure of the energy required to break the bond. A larger enthalpy means a stronger bond.

question

Lone pairs repel...

answer

More than bond pairs.

question

Electronegativity

answer

A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.

question

Permanent dipole

answer

A small charge difference that doesn't change across a bond.

question

How are induced dipole-dipole forces formed?

answer

The movement of electrons in shells causes an uneven distribution of charge this results in an instantaneous dipole. This induces a dipole in a neighbouring molecule and small induced dipoles attract one another.

question

Explain why ice is less dense than water.

answer

Water expands when it freezes because the hydrogen bonds become rigid forming a fixed open lattice with space in between making it less dense.

question

Explain why water has higher than expected melting and boiling points

answer

Hydrogen bonds are the strongest intermolecular forces so more energy is ended to break the forces between water molecules.

question

Diamond

answer

Has a tetrahedral structure held together by strong covalent bonds throughout the lattice.

question

Graphite

answer

Has a structure composed of hexagonal layers, each layer is held by weak intermolecular forces. It has delocalised electrons, so is a good conductor of electricity.

question

Graphene

answer

A single layer of graphite, made of hexagonally arranged carbon atoms. Each carbon atom has 3 strong covalent bonds to 3 other carbon atoms. It has delocalised electrons so is a good conductor of electricity.

question

Simple molecules

answer

Molecules that contain only a few atoms held together by strong covalent bonds (e.g. Iodine or Bromine)

question

Why do simple molecules have low melting and boiling points?

answer

There are only London forces between molecules which are weak and don't need much energy to be overcome.

question

Non-polar molecules are soluble in...

answer

Non-polar solvents.

question

Polar molecules are soluble in...

answer

Polar solvents.

question

Oxidation

answer

Loss of electrons and increase in oxidation number.

question

Reduction

answer

Gain of electrons and decrease in oxidation number.

question

Redox reaction

answer

A reaction involving both reduction and oxidation.

question

Reducing agent

answer

A reagent that reduces (adds electrons to) another species.

question

Oxidising agent

answer

A reagent that oxidises (takes electrons from) another species.

question

What are the factors affecting ionisation energy?

answer

Atomic radius, electron shielding and nuclear charge.

question

Electron shielding

answer

The repulsion between inner shell electrons and outer shell electrons which reduces the attraction between the nucleus and outer electrons.

question

Trends in ionisation energy down a group

answer

The first ionisation energies decrease since electron shielding and atomic radii increase and thus there is a decrease in attraction between outer electrons and the nucleus.

question

Trends in ionisation energy across a period

answer

The first ionisation energy increases as nuclear charge increases while atomic radii decreases and electron shielding remains the same and thus there is an increase in attraction between outer electrons and the nucleus.

question

Exceptions to the rule of ionisation energy

answer

1. Slight drop between group 12 and 13 as the outermost electron in group 12 is in the 2s sub-shell while the outermost electron in group 13 is in the 2p sub-shell. The 2p sub-shell is in a higher energy level so it is easier to remove and ionisation energy is lower. 2. Slight drop between groups 15 and 16. Outermost electron in both groups is in 2p sub-shell but it is unpaired in 15 and paired in 16. The pairing in group 16 causes repulsion so the outermost electron is easier to remove and ionisation energy is lower.

question

Trend in boiling points down group 17

answer

Boiling point increases because the number of electrons increases so there are more London forces and more energy is needed to break them.

question

Reaction of Cl2 or Br2 with I- observation

answer

Orange/brown solution OR purple in organic.

question

Reaction of Cl2 with Br- observation

answer

Yellow solution OR orange in organic.

question

Disproportionation

answer

Where an element is both oxidised and reduced in the same redox reaction.

question

Chloride observation with AgNO3

answer

White precipitate forms.

question

Chloride observation with NH3

answer

White precipitate dissolves on the addition of either dilute or concentrated NH3.

question

Bromide observation with AgNO3

answer

Cream precipitate forms.

question

Bromide observation with NH3

answer

Cream precipitate doesn't dissolve with dilute NH3 but does dissolve with concentrated NH3.

question

Iodide observation with AgNO3

answer

Yellow precipitate forms.

question

Iodide observation with NH3

answer

Yellow precipitate doesn't dissolve with either dilute or concentrated NH3.

question

Cl2 + H2O -->

answer

HClO + HCl

question

Equation for making bleach

answer

Cl2 + 2NaOH ---> NaCl + NaClO + H2O

question

Down group 2...

answer

Solubility and pH increases.

question

Test for carbonates

answer

Add nitric acid and bubble the gas given off through lime water. The lime water should go cloudy if a carbonate is present.

question

Test for sulfates

answer

Add barium nitrate/ carbonate/ chloride and if a sulfate is present then BaSO4 will form which is a white precipitate.

question

Test for ammonium

answer

Add aqueous sodium hydroxide and heat the solution to release the soluble ammonia gas produced. Test the gas with moist litmus paper which will turn blue if ammonium was present.

question

What order do we carry out the qualitative analysis tests?

answer

Carbonates Sulfates Halides

question

Standard electrode potential

answer

The tendency to be reduced and gain electrons compared with a standard hydrogen half-cell at 298K, 100KPa and with concentrations at 1.00 mol dm3.

question

E°Cell=

answer

E° most positive - E° most negative

question

The more negative the E°Cell, the...

answer

Greater the tendency to release electrons.

question

When using E°Cell values to predict feasible reactions, the most negative half equation always goes in...

answer

Reverse.

question

Non-rechargeable cells (primary cells) provide electrical energy until...

answer

The chemicals are used up.

question

Rechargeable cells (secondary cells) contain chemicals that react which can be reversed by...

answer

Recharging (e.g. Lithium ion or lithium-polymer batteries used in laptops.

question

Fuel cells continue to provide electricity provided there is a...

answer

Continuous supply of fuel and oxygen.

question

What is the overall cell reaction equation for fuel cells?

answer

H2 (g) + 1/2 02 (g) ---> H2O (l)

question

Transition element

answer

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

question

Which d block elements are not transition elements?

answer

Scandium and zinc.

question

Electron configurations of chromium and copper.

answer

Chromium: [Ar]4s13d5 (to minimise repulsion) Copper: [Ar]4s13d10

question

Chemical properties of transition elements.

answer

1. Variable oxidation states. 2. The have coloured compounds as they have coloured ions. 3. They act as catalysts.

question

Transition metal catalyst in the Haber process.

answer

Iron

question

Transition metal catalyst in the contact process.

answer

Vanadium oxide (V2O5)

question

Transition metal catalyst in the reaction of zinc and acids.

answer

Cu2+ ions

question

Transition metal catalyst in hydrogenation.

answer

Nickel

question

Transition metal catalyst in the decomposition of hydrogen peroxide.

answer

MnO2

question

Complex ion

answer

A transition metal ion bonded to one or more ligand by coordinate bonds.

question

Ligand

answer

A molecule or ion that can donate a pair of electrons to the transition metal.

question

Coordination number

answer

The total number of coordinate bonds formed between a central metal ion and ligands.

question

Complexes containing nickel, platinum, gold or silver form...

answer

Square planar complexes.

question

Describe the use of cis-platin as an anti-cancer drug.

answer

Cis-platin binds to the cells' DNA and prevents replication of cancer cells.

question

Bidentate ligand

answer

The ligand has 2 atoms which each have a lone pair of electrons that are donated to a central metal ion so it forms two coordinate bonds.

question

Optical isomers

answer

Non-superimposable mirror images of each other.

question

Observation: Cu2+ + 2OH- ---> Cu(OH)2

answer

Pale blue solution forms pale blue precipitate.

question

Observation: Cr3+ + 3OH- ---> Cr(OH)3

answer

Purple solution forms grey green precipitate.

question

Observation: Fe2+ + 2OH- ---> Fe(OH)2

answer

Pale green solution forms green precipitate that turns rusty brown in air.

question

Observation: Fe3+ + 3OH- ---> Fe(OH)3

answer

Pale yellow solution forms rusty brown precipitate.

question

Observation: Mn2+ + 2OH- ---> Mn(OH)2

answer

Pale pink solution forms light brown precipitate that darkens in air.

question

Cr(OH)3 is soluble in excess sodium hydroxide and forms a...

answer

Dark green solution.

question

What is the observation when excess ammonia is added to [Cu(H2O)6]2+?

answer

Dark blue solution forms.

question

What is the observation when excess ammonia is added to [Cr(H2O)6]3+?

answer

Purple solution forms.

question

Ligand substitution reaction

answer

When one ligand in a complex ion is replaced by another ligand.

question

Observation when Cu2+ and concentrated HCl are reacted.

answer

Pale blue solution turns to a green solution and finally a yellow solution.

question

Explain, in terms of ligand substitution, why carbon monoxide is so dangerous to humans.

answer

Carbon monoxide binds to the same site as oxygen would but forms a stable complex so doesn't break away. This makes the haemoglobin unable to transfer anymore oxygen.

question

Buffer

answer

A system that minimises pH changed when small amounts of an acid or a base are added.

question

Equivalence point

answer

The exact volume of solution required to neutralise a given volume of the other solution.

question

Enthalpy of neutralisation

answer

The enthalpy change that occurs when an acid and a base react to form one mole of water.

question

Half-life

answer

The time taken for the concentration of a reactant to reduce by half.

question

Gradient

answer

-Ea/R

question

Y intercept

answer

ln A

question

Ea (activation energy)

answer

-gradient x R

question

A (pre-exponential factor)

answer

e to the y intercept

question

Rate of reaction

answer

The decrease in concentration of reactants in a given unit of time.

question

Calculating gradient from a graph

answer

Difference in y/ difference in x

question

Experimental techniques used to measure rate of reaction

answer

1. Monitoring by gas collection 2. Monitoring by mass loss 3. Monitoring with a colorimeter 4. Iodine clocks

question

Overall order of a reaction

answer

The overall effect of the concentrations of all reactants on the rate of reaction.

question

Rate constant

answer

The number that mathematically converts between the rate of reaction, concentration and orders.

question

Rate=

answer

k[A][B]

question

Zero order rate-concentration graph

answer

Rate is unaffected by changes in concentration (straight horizontal line).

question

First order rate-concentration graph

answer

Rate is directly proportional to the reactant concentration (straight diagonal line).

question

Second order rate-concentration graph

answer

Rate is proportional to the reactant concentration squared (curved line getting steeper).

question

Half-life of first order reactants are..

answer

Constant.

question

Zero order concentration-time graph

answer

Concentration decreases at a constant rate (straight diagonal line).

question

First order concentration-time graph

answer

Concentration halves in regular time intervals (curved line decreasing).

question

Second order concentration-time graph

answer

Concentration decreases rapidly, but the rate of decrease then slows down (curved line steeply decreasing).

question

Reaction mechanism

answer

The series of steps that make up an overall reaction.

question

Rate determining step

answer

The slowest step in the sequence of a multi-step reaction.

question

Initial rate is approximately proportional to

answer

1/t

question

Rate constant of a first order reaction calculation

answer

k=ln2/half-life

question

pH=

answer

-log[H+]

question

Ka=

answer

[H+][A-]/[HA]

question

Weak acids: [H+]=

answer

Square root of [HA]xKa

question

pKa=

answer

-log(Ka)

question

Kw=

answer

[H+][OH-]

question

Buffer solutions: [H+]=

answer

Ka x [HA]/[A-]

question

How does a buffer solution work when an acid is added?

answer

[H+] increases. The H+ ions react with the conjugate base, A-. The equilibrium position shifts to the left, removing most of the H+ ions.

question

How does a buffer solution work when a base is added?

answer

[OH-] increases. The small concentration of H+ reacts with the OH- ions. H+ + OH- ---> H2O. HA dissociates, shifting the equilibrium to the right to restore most of the H+ ions.

question

Carbonic acid-hydrogencarbonate buffer system

answer

H2CO3 ---> H+ + HCO3-

question

Kc=

answer

[products]/[reactants]

question

Dynamic equilibrium

answer

Exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change.

question

Homogenous equilibrium

answer

An equilibrium with species that all have the same state.

question

Heterogeneous equilibrium

answer

An equilibrium with species that have different states.

question

Solid or liquid

answer

When you write the Kc for a heterogeneous reaction, don't include anything that is...

question

Mole fraction=

answer

Number of moles of gas A/total number of moles in gas mixture

question

Partial pressure=

answer

Mole fraction x total pressure

question

Kp=

answer

p(A) x p(B)/ p(C)

question

Bigger

answer

If more product is formed, K is...

question

Smaller

answer

If more reactants are formed, K is...

question

Increase

answer

If the reaction is endothermic, a rise in temperature will make K...

question

Decrease

answer

If the reaction is exothermic, a rise in temperature will make K...

question

Le Chatelier's principle

answer

If a system in dynamic equilibrium is subject to change, the position of equilibrium will shift to minimise the effect of this change.

question

Kc can only be affected by

answer

Temperature

question

Ozone depletion

answer

Cl + O3 ---> ClO + O2 ClO + O ---> Cl + O2 O3 + O ---> 2O2

OCR A Level Inorganic Chemistry – Flashcards

Unlock all answers in this set

Haven't found what you were looking for?

Search for samples, answers to your questions and flashcards