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98 Cards in this Set
- Front
- Back
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Rate of reaction
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The change in concentration of a reactant OR product per unit of time
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Order
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The power to which the concentration of the reactant is raised in the rate equation
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Rate constant, k
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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)
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Half-life
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The time taken for the concentration of a reactant to reduce by half
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Rate-determining step
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The SLOWEST STEP in the reaction mechanism of a multi-step reaction
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The half-life if a first-order reaction is ___________ of the concentration
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independent
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Zero order
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First Order
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Second order
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Kc =
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PRODUCTS/REACTANTS
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What is the effect on Kc on an increase in temperature for an exothermic reaction?
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Kc DECREASES
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What is the effect on Kc on an increase in temperature for an endothermic reaction?
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Kc INCREASES
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How is Kc affected by changes in concentration or pressure or by a catalyst?
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It isn't affected!
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What is an acid?
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A species that can donate a proton
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What is a base?
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A species hat can accept a proton
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What is an acid-base pair?
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A pair of two species that transform into each other by gain or loss of a proton
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What is the difference between a strong and weak acid?
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A strong acid completely dissociates in solution whereas a weak acid partially dissociates.
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What does Ka show?
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The extent of acid dissociation
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Weak acid, Ka =
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[H+][A-]/[HA]
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Large Ka =
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Large extent of dissociation - strong acid
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A high value of Ka means a ___ value of pKa
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Low
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The smaller the pKa the stronger/weaker the acid
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Stronger
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pKa =
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-log(Ka)
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pH =
10^-pH = |
-log[H+]
[H+] |
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Kw = (in words)
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Ionic product of water
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Kw = (expression)
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[H+][OH-]
At 25*C = 1x10^-14 |
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[H+] (strong monobasic acid) =
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[HA]
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[H+] (weak monobasic acid) =
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sqrt(Ka * [HA])
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[H+] (strong base) =
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Kw/[OH-]
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HCOOH <--> H+ + COO-
Ka = |
[H+][COO-]/[HCOOH]
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The stronger the acid, the _______ the value of Ka and the _______ the value of pKa
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The stronger the acid, the GREATER the value of Ka and the SMALLER the value of pKa
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What is a buffer solution?
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A system that minimises pH changes on addition of small amounts of an acid or base
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How can one make a buffer solution?
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A weak acid and a salt of the weak acid
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[H+] (buffer) = (2)
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Ka * [acid]/[salt]
OR pKa + log([salt]/[acid]) |
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Define: Enthalpy change of neutralisation
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The energy change that accompanies the neutralisation of an aqueous acid by an aqueous base to form one mole of water under standard conditions.
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Define: Lattice enthalpy
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The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions.
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Explain the three trends in lattice enthalpy:
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-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) |
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ΔH(solution) =
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ΔH(hyd) - ΔH(latt)
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Define enthalpy change of solution
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The enthalpy change when 1 mole of a compound is completely dissolved in water under standard conditions
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Define enthalpy change of hydration
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The enthalpy change when 1 mole of isolated gaseous ions is dissolved in water to form 1 MOLE of aqueous ions under standard conditions
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What is entropy?
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A measure of the 'disorder' of a system.
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A system becomes energetically more stable when it becomes more/less disordered?
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more
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Which is more entropic - solid or gas?
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Gas
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What happens to entropy when a solid lattice dissolves?
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It increases
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What happens to entropy when the number of gas particles decreases?
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Entropy decreases
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ΔS =
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ΔS = S(products) - S(reactants)
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What determines the tendency of a process to take place? (3)
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The temperature
The entropy change The enthalpy change |
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What is ΔG? What value must it take for spontaneous reactions?
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The free energy change of a system, it must be negative for a reaction to proceed spontaneously.
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ΔG =
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ΔH - TΔS
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How can endothermic reactions (positive ΔH) take place spontaneously? KEY QUESTION
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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. |
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What is the oxidation number?
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A measure of the number of elections that an atom uses to bond with atoms of another element.
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What is a reducing agent?
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A reagent that reduces (adds electrons to) another species
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Define 'standard electrode potential of a half cell'
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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
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How does a fuel cell create a voltage?
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It uses the energy from the reaction of a fuel with oxygen
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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 |
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How can hydrogen be stored in FCVs?
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As a liquid under pressure
ADsorbed on the surface of a solid material ABsorbed within a solid material |
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What are the limitations of hydrogen fuel cells? (3) - Get 3 points!
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Storage and transport
Limited lifetime, high production costs Use of toxic chemicals in their production |
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Hydrogen is an energy carrier, not an energy...
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source
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What are the limitations of a hydrogen economy? (3)
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Public and political acceptance of hydrogen as a fuel
Handling and maintenance of hydrogen systems Initial manufacture of hydrogen (energy requiring) |
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Colour: Cu2+
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Blue
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Colour: Cu(OH)2
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Blue
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Colour: Fe2+
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Pale green
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Colour: Fe(OH)2
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Green
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Colour: Fe3+
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Yellow/orange
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Colour: Fe(OH)3
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Red-brown/rust
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Colour: Co2+
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Pink
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Colour: Co(OH)2
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Blue-green --> Pink
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What is a ligand?
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A molecule or ion that can donate a pair of electrons with the transition metal ion to form a coordinate bond.
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What is a complex ion?
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A transition metal ion bonded to one or more ligands by coordinate bonds.
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What is the coordination number?
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The total number of coordinate bonds formed between the central metal ion and any ligands
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What is an example of a complex with a sixfold coordination number and octahedral bonding?
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[Cu(H₂O)₆]²⁺
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What is a bidentate ligand? What's an example of one?
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A ligand that can donate two lone pairs of electrons to the central metal ion to form two coordinate bonds.
'en' (NH2CH2CH2NH2) |
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What is the bond angle between the two groups of a cis isomer?
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90*
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What is the bond angle between the two groups of a trans isomer?
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180*
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What is the bond angle in a tetrahedral shape and when does tetrahedral bonding occur?
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109.5*, and when all the groups are the same(?)
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What is required for optical isomerism? (3)
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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-) |
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What is the use of cis-platin? How does it act?
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It is an anti-cancer drug and its acts by binding to DNA in cancer cells, thus preventing division.
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Colour: [Cu(H2O)6]2+
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Pale blue
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Colour: [Cu(NH3)4(H2O)2]2+
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Deep blue
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Colour: [CuCl4]2-
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Yellow
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Colour: [Co(H2O]6]2+
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Pink
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Colour: [CoCl4]2-
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Blue
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What's special about the bonding in [Cu(NH3)4(H2O)2]2+?
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It's a 'distorted octohedral' shape with the Cu-H2O bonds longer than the rest.
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[Cu(H2O)6]2+ + 4NH3 <-->
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[Cu(NH3)4(H2O)2]2+ + 4H2O
Remember: aqueous |
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[Cu(H2O)6]2+ + 4Cl- <-->
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[CuCl4]2- + 6H2O
Remember: aqueous |
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[Co(H2O)6]2+ + 4Cl- <-->
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[CoCl4]2- + 6H2O
Remember: aqueous |
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When initially adding copper(II) ions to HCl, what is the colour change?
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Green (then yellow)
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Why do only four Cl molecules bind to an ion instead of six?
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They are larger and cannot fit six
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What initially happens on addition of aqueous copper(II) ions and ammonia?
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The solution turns blue from the precipitate of copper(II) hydroxide (Cu(OH)2). Cu reacts with OH- ions in the solution.
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What is the importance of iron in haemoglobin?
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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
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Why is CO toxic?
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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.
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HbO2 + CO <-->
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HbCO + O2
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What is the stability constant?
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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 |
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What does a high value of K(stab) tell you?
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That the equilibrium lies to the right and is stable.
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What is important to omit in K(stab)?
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The concentration of water
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In the redox equation of Mn and F2, what is the ratio?
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1 Mn to 5 Fe2+
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What is the colour of MnO4- ions?
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Purple
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In the redox reaction of Mn and Fe - what colour is the end point?
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Pink
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