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98 Cards in this Set

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Rate of reaction
The change in concentration of a reactant OR product per unit of time
Order
The power to which the concentration of the reactant is raised in the rate equation
Rate constant, k
The constant that links the rate of reaction with the concentrations of the reactants (raised to the powers of their orders in the rate equation)
Half-life
The time taken for the concentration of a reactant to reduce by half
Rate-determining step
The SLOWEST STEP in the reaction mechanism of a multi-step reaction
The half-life if a first-order reaction is ___________ of the concentration
independent
Zero order
First Order
Second order
Kc =
PRODUCTS/REACTANTS
What is the effect on Kc on an increase in temperature for an exothermic reaction?
Kc DECREASES
What is the effect on Kc on an increase in temperature for an endothermic reaction?
Kc INCREASES
How is Kc affected by changes in concentration or pressure or by a catalyst?
It isn't affected!
What is an acid?
A species that can donate a proton
What is a base?
A species hat can accept a proton
What is an acid-base pair?
A pair of two species that transform into each other by gain or loss of a proton
What is the difference between a strong and weak acid?
A strong acid completely dissociates in solution whereas a weak acid partially dissociates.
What does Ka show?
The extent of acid dissociation
Weak acid, Ka =
[H+][A-]/[HA]
Large Ka =
Large extent of dissociation - strong acid
A high value of Ka means a ___ value of pKa
Low
The smaller the pKa the stronger/weaker the acid
Stronger
pKa =
-log(Ka)
pH =

10^-pH =
-log[H+]

[H+]
Kw = (in words)
Ionic product of water
Kw = (expression)
[H+][OH-]

At 25*C = 1x10^-14
[H+] (strong monobasic acid) =
[HA]
[H+] (weak monobasic acid) =
sqrt(Ka * [HA])
[H+] (strong base) =
Kw/[OH-]
HCOOH <--> H+ + COO-

Ka =
[H+][COO-]/[HCOOH]
The stronger the acid, the _______ the value of Ka and the _______ the value of pKa
The stronger the acid, the GREATER the value of Ka and the SMALLER the value of pKa
What is a buffer solution?
A system that minimises pH changes on addition of small amounts of an acid or base
How can one make a buffer solution?
A weak acid and a salt of the weak acid
[H+] (buffer) = (2)
Ka * [acid]/[salt]

OR

pKa + log([salt]/[acid])
Define: Enthalpy change of neutralisation
The energy change that accompanies the neutralisation of an aqueous acid by an aqueous base to form one mole of water under standard conditions.
Define: Lattice enthalpy
The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions.
Explain the three trends in lattice enthalpy:
-ΔH

More exothermic if ionic charge increases (increased CHARGE DENSITY on the ions - stronger attraction)

More exothermic if ionic radius decreases (Charge density increases if radius decreases, increased attraction)
ΔH(solution) =
ΔH(hyd) - ΔH(latt)
Define enthalpy change of solution
The enthalpy change when 1 mole of a compound is completely dissolved in water under standard conditions
Define enthalpy change of hydration
The enthalpy change when 1 mole of isolated gaseous ions is dissolved in water to form 1 MOLE of aqueous ions under standard conditions
What is entropy?
A measure of the 'disorder' of a system.
A system becomes energetically more stable when it becomes more/less disordered?
more
Which is more entropic - solid or gas?
Gas
What happens to entropy when a solid lattice dissolves?
It increases
What happens to entropy when the number of gas particles decreases?
Entropy decreases
ΔS =
ΔS = S(products) - S(reactants)
What determines the tendency of a process to take place? (3)
The temperature
The entropy change
The enthalpy change
What is ΔG? What value must it take for spontaneous reactions?
The free energy change of a system, it must be negative for a reaction to proceed spontaneously.
ΔG =
ΔH - TΔS
How can endothermic reactions (positive ΔH) take place spontaneously? KEY QUESTION
ΔG is still negative.
ΔS is also positive - e.g. when something dissolves in water their arrangement becomes more disordered

TΔS is larger than ΔH, so ΔG is negative and the reaction proceeds spontaneously.
What is the oxidation number?
A measure of the number of elections that an atom uses to bond with atoms of another element.
What is a reducing agent?
A reagent that reduces (adds electrons to) another species
Define 'standard electrode potential of a half cell'
The EMF of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1 mol dm^-3 and a gas pressure of 100 kPa
How does a fuel cell create a voltage?
It uses the energy from the reaction of a fuel with oxygen
Scientists in the car industry are developing fuel cell vehicles (FCVs) fuelled by:

What is the advantage of FCVs?
Hydrogen gas and hydrogen rich fuels

Less pollution and less CO2
Greater efficiency
How can hydrogen be stored in FCVs?
As a liquid under pressure

ADsorbed on the surface of a solid material

ABsorbed within a solid material
What are the limitations of hydrogen fuel cells? (3) - Get 3 points!
Storage and transport

Limited lifetime, high production costs

Use of toxic chemicals in their production
Hydrogen is an energy carrier, not an energy...
source
What are the limitations of a hydrogen economy? (3)
Public and political acceptance of hydrogen as a fuel

Handling and maintenance of hydrogen systems

Initial manufacture of hydrogen (energy requiring)
Colour: Cu2+
Blue
Colour: Cu(OH)2
Blue
Colour: Fe2+
Pale green
Colour: Fe(OH)2
Green
Colour: Fe3+
Yellow/orange
Colour: Fe(OH)3
Red-brown/rust
Colour: Co2+
Pink
Colour: Co(OH)2
Blue-green --> Pink
What is a ligand?
A molecule or ion that can donate a pair of electrons with the transition metal ion to form a coordinate bond.
What is a complex ion?
A transition metal ion bonded to one or more ligands by coordinate bonds.
What is the coordination number?
The total number of coordinate bonds formed between the central metal ion and any ligands
What is an example of a complex with a sixfold coordination number and octahedral bonding?
[Cu(H₂O)₆]²⁺
What is a bidentate ligand? What's an example of one?
A ligand that can donate two lone pairs of electrons to the central metal ion to form two coordinate bonds.

'en' (NH2CH2CH2NH2)
What is the bond angle between the two groups of a cis isomer?
90*
What is the bond angle between the two groups of a trans isomer?
180*
What is the bond angle in a tetrahedral shape and when does tetrahedral bonding occur?
109.5*, and when all the groups are the same(?)
What is required for optical isomerism? (3)
A complex with three molecules of a bidentate ligand

A complex with two molecules of a bidentate ligand and two molecules of a monodentate ligand

A complex with one hexadentate ligand ([Cu(EDTA)]2-)
What is the use of cis-platin? How does it act?
It is an anti-cancer drug and its acts by binding to DNA in cancer cells, thus preventing division.
Colour: [Cu(H2O)6]2+
Pale blue
Colour: [Cu(NH3)4(H2O)2]2+
Deep blue
Colour: [CuCl4]2-
Yellow
Colour: [Co(H2O]6]2+
Pink
Colour: [CoCl4]2-
Blue
What's special about the bonding in [Cu(NH3)4(H2O)2]2+?
It's a 'distorted octohedral' shape with the Cu-H2O bonds longer than the rest.
[Cu(H2O)6]2+ + 4NH3 <-->
[Cu(NH3)4(H2O)2]2+ + 4H2O

Remember: aqueous
[Cu(H2O)6]2+ + 4Cl- <-->
[CuCl4]2- + 6H2O

Remember: aqueous
[Co(H2O)6]2+ + 4Cl- <-->
[CoCl4]2- + 6H2O

Remember: aqueous
When initially adding copper(II) ions to HCl, what is the colour change?
Green (then yellow)
Why do only four Cl molecules bind to an ion instead of six?
They are larger and cannot fit six
What initially happens on addition of aqueous copper(II) ions and ammonia?
The solution turns blue from the precipitate of copper(II) hydroxide (Cu(OH)2). Cu reacts with OH- ions in the solution.
What is the importance of iron in haemoglobin?
It is the central ion in haemoglobin and forms four dative covalent bonds from the nitrogen atoms in a PORPHYRIN RING. It also binds to an AA on the globin molecule. The sixth ligand in the complex is OXYGEN
Why is CO toxic?
It binds to the central Fe2+ ion more strongly than oxygen and replaces it in the complex. Oxygen therefore cannot be carried around the body, causing ASPHYXIATION.
HbO2 + CO <-->
HbCO + O2
What is the stability constant?
The equilibrium constant for an equilibrium existing between a transiiton metal ion surrounded by water ligands and the complex formed when the same ion has undergone a ligand substitution.

Yeah
What does a high value of K(stab) tell you?
That the equilibrium lies to the right and is stable.
What is important to omit in K(stab)?
The concentration of water
In the redox equation of Mn and F2, what is the ratio?
1 Mn to 5 Fe2+
What is the colour of MnO4- ions?
Purple
In the redox reaction of Mn and Fe - what colour is the end point?
Pink