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Equilibria, Energetics and Elements P 2
P2
114
Chemistry
Undergraduate 1
01/13/2016

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Term
In a rate-concentration graph there is a single horizontal flat line, determine the order of the compound
Definition
Zero-order with respect to compound
Term
What is the formula for the rate equation?
Definition
Rate=k[A]^[B]^
Term
In a two step mechanism what is the name of the first step?
Definition
The rate determining step
Term
What are the reactants in the rate determining step?
Definition
The compounds found in the rate equation
Term
Produce a two-step mechanism for this:

H2 + 2ICl -> 2HCl + I2

rate=k[H2][ICl]
Definition
H2 + ICl -> HCl + HI
HI + ICl -> HCl + I2
Term
Define the term lattice enthalpy
Definition
The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions
Term
State the meaning of the term ligand
Definition
Donates an electron to a metal ion / forms a coordinate bond to a metal ion
Term
What is the difference between a strong acid and a weak acid?
Definition
A strong acid completely dissociates and a weak acid partially dissociates
Term
Explain what is meant by the term Bronsted-Lowry base
Definition
Proton acceptor
Term
Why is it difficult to predict if the lattice enthalpy of magnesium sulfide would be less/more exothermic than that of sodium oxide?
Definition
Mg2+ is smaller and Mg2+ has a greater charge
S2- is larger
But Mg2+ has stronger attraction and S2- has weaker attraction
Term
What is a property of cobalt(II) and cobalt(III) that is typical of transition ions?
Definition
They are catalysts or coloured
Term
CoSO4(aq) reacts with NaOH(aq) what is the transition element species formed? And what type of reaction is it?
Definition
Co(OH)2
Precipitation
Term
CoSO4(aq) reacts with HCl(aq) what is the transition element species formed? And what type of reaction is it?
Definition
CoCl4^2-
Ligand substitution
Term
Write an expression for Ka of HNO2
Definition
Ka=([H+][NO2-])/[HNO2]
Term
Ca(OH)2(aq) + HNO2(aq) write the overall equation and ionic equation
Definition
Ca(OH)2 + 2HNO2 -> Ca(NO2)2 + 2H2O
H+ + OH- -> H2O
Term
How does equilibrium allow a buffer to control pH?
Definition
Added alkali reacts with H+
Shifting equilibrium to produce more H+

Added acid reacts with conjugate base(salt)
Equilibrium shifts towards HA
Term
What is needed for testing cell potentials?
Definition
Voltmeter
Salt bridge
Electrode (Pt or metal)
1 mol dm^-3 concentration
Term
What are the three ways being developed to store hydrogen for fuel?
Definition
Absorption in a solution
Adsorption on a solid
Liquid under high pressure
Term
Write the equation that links free energy change with enthalpy change and temperature?
Definition
/\G=/\H - T/\S
Term
Why could an exothermic reaction occur at low temperatures but not at high temperatures?
Definition
T/\S is more negative as temperature increases
At high temperature T/\S is more negative than /\H
Term
When is a reaction feasible?
Definition
/\G<0 or /\G=0
Term
What is the formula for Kc?
Definition
[concentration of product]^mol / [concentration of reactant]^mol
Term
What does pressure, temperature and concentrations do to Kc?
Definition
Pressure and concentrations do not affect Kc
Only temperature affects Kc
The system increase/decreases products and reactants to maintain Kc
Term
Define lattice enthalpy
Definition
Formation of one mole of an ionic conditions from its gaseous ions under standard conditions
Term
Why do ionic compounds differ in melting points?
Definition
There is greater attraction from smaller ions
More (heat) energy to overcome attraction
Term
What happens when there is a decrease in entropy?
Definition
There is less disorder
Term
If enthalpy and entropy are both negative how will feasibility change as temperature increases?
Definition
Reaction becomes less feasible
/\G increases
T/\S becomes more negative
Term
How can you work out entropy?
Definition
Entropy of products - entropy of reactants
Term
What is the equation for /\G?
Definition
/\G=/\H-T/\S
Term
When does a reaction become feasible?
Definition
/\G=0
Term
Write an expression of Kc for 2CH4->C2H2 + 3H2
Definition
[C2H2][H2]^3/[CH4]^2
Term
What happens to the initial rate when temperature is increased?
Definition
Initial rate increases
Term
What happens to the initial rate when pressure is increased?
Definition
Initial rate increases
Term
What happens to the initial rate a catalyst is added?
Definition
Initial rate increases
Term
Give two examples of large-scale uses of hydrogen
Definition
Fuel cells
Manufacture of margarine
Making ammonia
Making HCl
Making methanol
Term
Why would a reaction take place in multiple steps?
Definition
Stoichiometry in rate equation does not match stoichiometry in overall equation
Collision unlikely with more than 2 ions
Term
Draw a rate concentration graph of something that is first order
Definition
[image]
Term
Draw a rate concentration graph of something that is second order
Definition
[image]
Term
How do convert pKa to Ka?
Definition
10^-pKa
Term
What are the two general equation for Ka of a weak acid?
Definition
Ka= ([H+][A-])/[HA] OR [H+]^2/[HA]
Term
What is the equation for pH?
Definition
pH=-log(H+)
Term
Why are Sc and Zn not transition elements?
Definition
A transition element has an ion with an incomplete d-orbital
Sc and Zn are not transition element
Sc3+ is 1s2 2s2 2p6 3s2 3p6
Zn2+ is 1s2 2s2 2p6 3s2 3p6 3d10
Sc3+ d-orbital is empty
Zn2+ d-orbital is full
Term
How does H2NCH2CH2NH2 act as a bidentate ligand?
Definition
Electron lone pair of N
Donates two electron lone pairs to a metal ion
Term
What would make a compound have stronger ionic bonds?
Definition
Greater ionic charge
Smaller ionic size
Term
What does a y=x rate-concentration graph show?
Definition
1st order with respect
Term
What is the formula for rate equation and what is k?
Definition
rate=k[]^order
k is the rate constant
Term
How can weak acid be proved by a single pH test?
Definition
Measured pH is > 0
Term
What is the acid dissociation constant?
Definition
Ka
Term
What is the formula for Ka of a weak acid?
Definition
Ka=([H+]²/[HA])
Term
What is the relation between the concentration of H+ and pH?
Definition
[H+]=10^-pH
Term
What is the equation for Kw?
Definition
Kw=[H+][OH-]
Term
What is a buffer formed from?
Definition
A weak acid and a salt of the weak acid
Term
What happens when acid is added to a buffer?
Definition
Conjugate base reacts with added acid
Equilibrium shifts to restore conjugate base (usually left)
Term
What happens when alkali is added to a buffer?
Definition
Weak acid reacts with added alkali
Equilibrium shifts to restore acid (usually right)
Term
What is needed to set up an electrochemical cell?
Definition
Voltmeter
Salt bridge
Electrodes
1 mol dm-3 solutions in each
Term
What reaction is on the right hand side of the electrochemical cell?
Definition
Reduction
Term
How is cell potential worked out?
Definition
E(positive terminal (left))-E(negative terminal (right))
Term
What carries the charge through the wire of an electrochemical cell?
Definition
e-
Term
What carries the charge through the solution of an electrochemical cell?
Definition
ions
Term
What is the main difference between an electrochemical cell and a fuel cell?
Definition
A fuel cell converts energy from the reaction of a fuel with oxygen into a voltage
Term
What is the overall reaction in a fuel cell?
Definition
2H2 + O2 -> 2H2O
Term
What are the ways to store hydrogen?
Definition
Under pressure as a liquid
Adsorbed on solid
Absorbed within solid
Term
Why is the use of hydrogen for fuel considered the same as fossil fuels?
Definition
Energy is needed to make the hydrogen
Term
What is the expression for Kc?
Definition
Kc=([products]^mol/[reactant]^mol[reactant]^mol)
Term
What side does equilibrium favour when pressure is increased?
Definition
The side with the least moles
Term
When pressure increases what happens to Kc?
Definition
Kc does not change
Increase in pressure causes the system to no longer be in equilibrium
So top of Kc expression increases and bottom decreases until Kc is reached
Term
What is another method other than using fossil fuels to produce hydrogen?
Definition
Electrolysis of water
Term
What is needed for a reaction to be feasible?
Definition
/\G < 0
Term
What is the expression for /\G?
Definition
/\G = /\H - T/\S
Term
What is the expression for /\S?
Definition
/\S = (sum of products) - (sum of reactants)
Term
If T/\S is negative why would an increase in temperature cause a reaction to not be feasible?
Definition
As temperature increases T/\S becomes more negative
Eventually /\G becomes positive
Term
What are the two transitional metals with a partially filled 4s sub-shell?
Definition
Chromium and copper
Term
What electrons get lost first in transitional metals?
Definition
4s electrons
Term
What is a ligand?
Definition
A molecule that donates an electron pair to a metal ion to form a coordinate bond
Term
How can a molecule act as a bidente ligand?
Definition
Lone pairs on two atoms
Donates two electron pairs
Forms two coordinate bonds
Term
What are the three ways to follow the rate of reaction?
Definition
Record gas volume
Observe colour changes
Electrical conductivity changes
Term
What is the reaction rate?
Definition
Change in amount of compounds per unit time
Term
What is the half life?
Definition
The time its takes for half of the reactant to be used up
Term
What has a constant half life?
Definition
First order reaction
Term
What is a clock reaction?
Definition
A reaction where you can easily measure the time before a product is formed
Term
What affects the rate constant (k)?
Definition
Temperature
Term
A higher temperature does what to the rate constant (k)?
Definition
Increases it
Term
How is equilibrium formed?
Definition
As reactants get used up forward reaction slows down
As more product is formed the reverse reaction speeds up
Till the rate of the forward reaction is the same as the reverse reaction
Term
What are the two main things needed for dynamic equilibrium?
Definition
A closed system
A constant temperature
Term
What is the only thing that affects Kc?
Definition
Temperature
Term
Why does temperature affect Kc?
Definition
Change means more product is formed
Kc will increase
Term
What do cells use as a buffer solution?
Definition
H2PO4- <-> H+ + HPO4^2-
Dihydrogen phosphate ions and Hydrogen phosphate ions
Term
What does the blood use as a buffer solution?
Definition
H2CO3 <-> H+ + HCO3-
Carbonic acid
Term
Whats a strong acid/strong alkali titration graph look like?
Definition
[image]
Term
Whats a strong acid/weak alkali titration graph look like?
Definition
[image]
Term
Whats a weak acid/strong alkali titration graph look like?
Definition
[image]
Term
Whats a weak acid/weak alkali titration graph look like?
Definition
[image]
Term
The horizontal line of a titration curve indicates?
Definition
Equivalence point
Neutralised
Term
What is methyl oranges pH of colour change? and what is the colour change?
Definition
Red to Yellow
3.1-4.4
Term
What is phenolphthalein pH of colour change? and what is the colour change?
Definition
Colourless to pink
8.3-10
Term
What are the properties of transition metals?
Definition
Form complex ions
Variable oxidation states
Coloured compounds
Good catalysts
Term
What is the colour change that accompanies
Cu2+ + 2OH- -> Cu(OH)2
Definition
Pale blue to blue precipitate
Term
What is the colour change that accompanies
Co2+ + 2OH- -> Co(OH)2
Definition
Pink to blue precipitate that goes back to pink
Term
What is the colour change that accompanies
Fe2+ + 2OH- -> Fe(OH)2
Definition
Pale green to dark green precipitate
Term
What is the colour change that accompanies
Fe3+ + 3OH- -> Fe(OH)3
Definition
Yellow to dark orange/brown precipitate
Term
What is a transition element?
Definition
Forms a stable ion with an incomplete d sub shell
Term
What is a complex ion?
Definition
A transition metal coordinately bonded to one or more ligands
Term
What is a coordinate bond?
Definition
Dative covalent bond where a shared pair of electrons come from the same atom
Term
What is a ligand?
Definition
A molecule that can donate a pair of electrons to form a coordinate bond
Term
What do you call a ligand with two lone pairs?
Definition
Bidentate
Term
What is the structure for platin?
Definition
NiCl2(NH3)2
Term
How is cis-platin used to treat cancer?
Definition
Binds to DNA of cancer cell
Prevents reproduction
Term
What is the reaction and colour change of aqueous copper(II) ions and ammonia?
Definition
[Cu(H2O)6]2+ + 4NH3 <-> [Cu(NH3)4(H2O)2]2+ + 4H2O

Pale blue to deep blue
Term
What is the reaction and colour change of aqueous copper(II) ions and chloride?
Definition
[Cu(H2O)6]2+ + 4Cl- <-> [CuCl4]2- + 6H2O

Pale blue to yellow
Term
What is the reaction and colour change of aqueous cobalt(II) ions and chloride?
Definition
[Co(H2O)6]2+ + 4Cl- <-> [CoCl4]2- + 6H2O

Pink to blue
Term
What is the reaction and colour change of aqueous cobalt(II) ions and ammonia?
Definition
[Co(H2O)6]2+ + 6NH3 <-> [Co(NH3)6]2+ + 6H2O

Pink to brown
Term
What does a larger Kstab mean?
Definition
Ion is very stable
Term
What is meant by stability constant?
Definition
Equilibrium constant for the formation of a complex ions from it constituent ions
Term
Draw the structure of haemoglobin
Definition
[image]
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