Further physical Flashcards by Chan Marco

Enthalpy

A value that represents heat content of system

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Enthalpy change of atomization

enthalpy change when 1 mol of gaseous atom is formed from an element in standard state

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Enthalpy change of hydration

enthalpy change when 1 mol of gaseous ions are dissolved in water

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Enthalpy change of solution

enthalpy change when 1 mol of solute is dissolved in water

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1st electron affinity

energy released when 1 mol of electron is added to 1 mol of gaseous atom, forming 1 mol of gasous 1- ions

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Lattice enthalpy

Formation of 1 mol of ionic lattice from 1 mol of gasous ions

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What is lattice enthalpy a measure of?

strength of ionic bonds in lattice

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Describle born-haber cycle diagram

atomization + Ionisation + electron affinity + ΔH(LE)
= enthalpy change of formation

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How to increase lattice enthalpy ?

1.↑ ionic charge ( ↑ p : e ratio )
2.↓ ionic radius ( ↓ dist. = ↑ attraction )

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0th order conc-time graph

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1st order conc-time graph

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2nd order conc-time graph

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0th order rate-conc graph

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1st order rate-conc graph

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2nd order rate-conc graph

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properties of 1st order conc-time graph

exponential decay
[constant half-life]

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how to find rate constant for 1st order reaction

k = ln(2) / t1/2

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2 methods of investigating rate

initial rate
continuous monitoring of conc.

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Describle measuring intial rate with
E.g. iodine clock

record time for color change
(e.g. colorless to blue-black)

initial rate = 1/time for color change

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Assumption made to record initial rate

no significant change in rate in the period recorded

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Describle how calorimetry is used to determine rate

certain wavelength of light is emitted to solution
absorbance is recorded
conc is monitored as proportional to absorbance

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Desrible lattice enthalpy cycle

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Describle enthalpy change of hydration cycle

ΔH(LE) + ΔH(solution) = ΔH(hydration)

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Factors that affects ΔH(hydration)

↑ionic charge
↓ionic radius

↑ionic density = ↑ attraction on H2O= ↓ΔH

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Affect of Δtemp on rate constant

As Temp↑, k↑ , rate↑

Homogenous eqm

eqm species all in **same** state

Hetrogenous eqm

eqm species have **different** states/ phase

How to determine Kc/Kp experiementally?

1. Mix known moles of reactant and acid 2. wait 3. then titrate one of the products to find the conc at eqm 4. then find all conc at eqm by stoichiometry

Factors that affect(/not) Kc/Kp

**Temp. ** Does not: 1. pressure 2. conc. (causes eqm to shift to restore value)

effect of temp on Kc | if LHS -> RHS is endo

1. eqm shifts to the right 2. to restore temp 3. ↑[products] ∴ ↑Kc

Define Bronsted-Lowry acid

A species that donates a proton

Define bronsted-Lowry bases

a species that accept proton

Define monobasic acid

A species that contains **1 ionisable hydrogen atoms** per molecule

Assumptions made when doing weak acid calculations

1. [HA]i = [HA]eqm 2. [H+]=[A-]

Ka equation for strong acid

pKa to Ka conversions

pka = -log Ka

How to find pH of strong bases

1. Find the conc of [OH-] 2. use Kw = [H+][OH-] 3. find [H+]

2 methods of preparing buffer

1. weak acid + its salt (conjugate base) 2. weak acid + strong base

Define buffer solution

minimises change in pH when small amount of acid/base is added

# Buffer senario How does buffer minimises change in pH when **acid** is added | (3)

1. [H+] ↑ 2. eqm shifts to the left 3. ↓ [H+]

How does buffer minimises change in pH when **base** is added | (5)

1. [OH-] increases 2. H+ + OH- -> H20 3. [H+] ↓ 4. eqm shifts to the LHS 5. restores [H+]

How to set up neutralisation reaction | (5)

1. Add measured volume of acid/base into conical flask 2. place electrode (of pH meter) into solution 3. Add base/acid to burrette 4. add 1 cm3 at a time 5. go to dropwise when pH changes rapidly

What are pH indicators? How do they change color

Weak acid conjugate acid-base have different color

what is the difference between end point and equivilance point

End point - physical observation equivilance point - theroritical, n(titrate) =n(analyte)

How to choose an indicator?

indicator range aligns with vertical section pKa in the pH range of color change

why does pKa tell the range of the indicator

1.[A-] = [HA] 2.Ka = [H+] 3. pH = -log[H+] position of the end point

Define Isoelectric point

pH at which a particular molecule carries no net electrical charge

# redox chem MnO4 2- reduced to ...

Mn 2+ [+7] -> [+2]

# redox chem Fe 2+ oxidised to ...

Fe 3+ [+2] -> [+3]

# redox titration which acid is used to dissolve iron sulphate

sulphuric acid

# redox titration Why other acids are not suitable to dissolve | in manganate + iron sulphate

Maybe oxidised or act as oxidising agent for other substance

# Redox chem iodine and thiosulphate redox eq.

What is in the conical flask for following redox + purpose | iodine + thiosulphate

excess KI oxidising agent to generate Iodine

steps to determine end point | iodine + thiosulphate

1. turning from yellow-brown to yellow 2. add starch 3. blue-black End point at colourless

End point for iron + manganate

purple to 1st permanent pale pink colour

What is calorimetry measure

Wavelength of light - depending on color

Define transition metal

d-block element that forms at least 1 ion with incomplete d-subshell

2 d-block element that is not transition metal

Sc - only form Sc 3+ Zn - only form Zn 2+

two transition element that don't have 4s ^2

copper and chromium [4s^1]

Bond angle of square planar

90 deg

how many water ligand is formed in aqueos metal complex ?

Colour of Cr 3+ (aq)

violet

Colour of Fe 2+ (aq)

green

Colour of Fe 3+ ion (aq)

yellow

Colour of Mn 2+ (aq)

pale pink

colour of Cu 2+ ion (aq)

Blue

Two transition aqueous ion with same colour with the OH substituted ligand

Fe 2+ and Cu 2+

Colour of Cr (OH)3 p.p.

grey-green

colour of Fe (OH)2 p.p.

green

colour of Fe (OH)3 p.p.

brown

colour of Mn (OH)2 p.p.

pale brown

colour of Cu(OH)2 p.p.

Blue p.p.

transition metal that has a colour change in **ex. OH-**

Cr 3+ -> dark green

2 transition metals that changes colour in **ex. NH3 **

Cr 3+ - purple Cu 2+ - dark blue

3 types of transition metal reaction

1. ligand substitution 2. p.p. reaction 3. redox

3 ligand substitution reaction

1. Cr (aq) complex + NH3 ex. 2. Cu (aq) complex + NH3 ex. 3. Cu (aq) complex + 4 Cl- ligands

what is the **formula + coordination no** of the complex formed from Cu(H2O)6 + 4Cl-

[CuCl4]2-

colour of [CuCl4]2-

yellow

What is Haem and its function

1. iron complex 2. forms ligand bonds with O2 3. also bond with CO ligand - but stronger

what is the oxidising agent of Fe 3+ (to Fe 2+)

MnO4- ( goes to Mn 2+ )

reducing agent of Fe 3+ (to Fe 2+)

I- (iodide ion)

colour of Fe 3+

orange-brown

colour of Fe 2+

pale-green

colour change of iron-manganate titration

purple to colourless

colour of Cr^3+ in redox

green

colour of Cr2O7^2-

orange

colour of Cr 2+

Blue

Colour of Copper iodide p.p. (CuI)

white