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Chemistry SL > Chapter 4, 5, 6, & 7 > Flashcards

Chapter 4, 5, 6, & 7 Flashcards

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1
Q

What does the strength of a metallic bond depend on?

A
  • the CHARGE of the ions
  • the RADIUS of the metal ion

sometimes the arrangement of the atoms is also important

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2
Q

does melting point increase or decrease from Al to Sn? (weird example)

A

it decreases due to arrangement of atoms

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3
Q

define alloy

A

homogenous mixtures of 2 or more metals, or of a metal & non-metal

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4
Q

when a substance more volatile?

A

when the attractive forces are weaker

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5
Q

why do longer chain alcohols become progressively less soluble in water?

A

due to the long hydrocarbon chains preventing hydrogen bonding b/w water molecules

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6
Q

What determines the melting points of ionic compounds?

A
  • the way the particles in the crystal state are packed together
  • impurities within the ionic compound
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7
Q

how do impurities affect ionic compounds?

A

they weaken the ionic compounds & result in lower melting points

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8
Q

why is ethanol a good solvent for substances?

A

because it has both polar & non-polar regions

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9
Q

what are negative ions sometimes known as?

A

they are known as acid radicals as they are formed when an acid loses one or more H+ ions

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10
Q

which are the strongest types of repulsions?

A

long-pair lone-pair repulsions are strongest due to the lone pairs being closer to the central nucleus & thus closer to the bonding electrons

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11
Q

what causes a polar bond?

A

may result from one end of the molecule being electron rich

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12
Q

give examples of resonance hybrids

A

ozone, benzene, carbonate ion, nitrate ion, & ethanoate ion

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13
Q

List a few allotropes of carbon

A

diamond, graphite, graphene, C60 fullerene

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14
Q

characteristics of diamond

A

Giant covalent
Tetrahedral
Each C is joined to 4 others
Very high melting/boiling point
Does NOT conduct electricity
HIGHEST THERMAL CONDUCTIVITY
Insoluble in water or organic solvents
NO delocalised electrons

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15
Q

characteristics of graphite

A

Giant covalent
Trigonal planar
Hexagonal ring layers held tog. by weak LDF
High melting/boiling point
Conducts electricity + good lubricant (pencils)
High thermal conductivity
Insoluble in water & polar solvents
Delocalised electrons

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16
Q

characteristics of graphene

A

Giant covalent
Trigonal planar
Single layer of hexagonally arranged C atoms
High melting / boiling point
Conducts electricity
High thermal conductivity
Insoluble in water
Delocalised electrons

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17
Q

C60 fullerene

A

Molecular
Hexagons & pentagons – looks like ball
melting/boiling point not at high as other allotropes due to molecular structure - is soft
Does NOT conduct electricity (delocalised electrons cannot move b/w molecules)
Insoluble in water but soluble in some organic solvents like benzene
Delocalised electrons

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18
Q

characteristics of Silicon dioxide

A

Giant covalent
Tetrahedral around Si, bent around O
Each Si joined to 4 O atoms, each O joined to 2 Si atoms
High melting & boiling point
Does NOT conduct electricity
Very poor thermal conductor
Insoluble in water
NO delocalised electrons

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19
Q

are bonds in products or reactants stronger for EXOTHERMIC reactions?

A

bonds in products are stronger than bonds in reactants because heat is given out to surroundings

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20
Q

what are standard conditions?

A

101 kPa, 298 K

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21
Q

difference b/w heat & temperature

A

HEAT = total energy in a given amount of substance –> depends on amount of substance present

TEMPERATURE = average kinetic energy of substance, but is independent of amount of substance present

(two substances w/ dif volume could have same temp but dif heat)

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22
Q

Hess’s law

A

the enthalpy change for a reaction depends on the difference between the enthalpy of the products & the enthalpy of the reactants - is independent of the reaction pathway

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23
Q

define standard enthalpy change of formation

A

the enthalpy change when 1 mole of the compound is formed from its elements in their STANDARD STATES at STP

24
Q

what is the enthalpy change of formation of Mg in standard state?

A

0, since it is an element in standard form

25
Q

define standard enthalpy change of combustion

A

enthalpy change when 1 mole of a substance is completely combusted in oxygen at STP

26
Q

condition for calculating bond enthalpy

A

calculated in gaseous state

27
Q

define average bond enthalpy

A

the energy needed to break 1 mole of a bond in a gaseous molecule AVERAGED over similar compounds

e.g. must be gaseous NOT diatomic (F2)

28
Q

limitations of using bond enthalpies

A
  • the energy of a particular bond will vary in dif compounds
  • if more energy is required to convert gaseous water to liquid (to keep it in its standard state), this may require even more energy
29
Q

significance of difference in bond enthalpies b/w ozone (resonance) & oxygen (double bond)?

A

it helps to protect us from the sun’s UV rays

The ozone layer protects the Earth from damaging UV radiation by absorbing both high & low energy UV light to break these bonds

Ozone absorbs lower frequency / energy than oxygen & its bond is weaker

30
Q

rate of production of ozone = ?

A

the rate of ozone destruction

31
Q

what causes holes in the ozone layer?

A

human-made pollutants such as CFCs & oxides of nitrogen can disrupt this process of ozone production

32
Q

how can rate of reaction b/w CaCO3 & HCl be determined?

A
  • by measuring concentration of HCl
  • volume of CO2 produced
  • reduction in mass
33
Q

the faster a particle moves . . .

A

the more KINETIC energy it possesses

34
Q

Collision theory

A
  • particles must collide
  • with appropriate geometry/orientation
  • collide w/ sufficient energy to bring about the reaction
35
Q

why does temperature result in higher reaction rates?

A

more of the colliding particles will possess the necessary activation energy resulting in more successful collisions

36
Q

why does the rate of reactions get slower as reaction proceeds?

A

the reactants get used up as their concentration decreases

37
Q

transition point is . . .

A

the point at which products can form

38
Q

slower reactions tend to have . . .

A

HIGHER Ea values

39
Q

Faster reactions tend to have . . .

A

LOWER Ea values

40
Q

does temperature have an effect on the Ea of a reaction?

A

NO

41
Q

what causes the increase in average kinetic energy when temperature is raised?

A

the very high velocity

42
Q

What is dynamic equilibrium?

A
  • concentration of products & reactants is CONSTANT
  • forward & reverse reaction rates are EQUAL
43
Q

example of physical equilibrium

A

condensation & vaporisation

44
Q

requirement for equilibrium?

A

all reactants and products must be in SAME PHASE during equilibrium

45
Q

closed system is important for equilibrium because. . .

A

neither matter nor energy can be lost or gained from system - MACROSCOPIC PROPERTIES ARE CONSTANT

46
Q

examples of macroscopic properties

A

pressure, volume, temperature

47
Q

What is Kc vs Qc?

A

Kc (constant at specific temperature) - how far a reaction proceeds

Qc - in which direction the reaction will proceed to reach equilibrium

48
Q

Le Chatelier’s principle

A
  • if a system at equilibrium is subjected to a small change, the equilibrium tends to shift so as to minimise the effect of that change
49
Q

what is the value of Kc in esterification reactions?

A

it is 4 at 100C

50
Q

if pressure is increased. . .

A

the position of equilibrium shifts to the side with less moles (MUST BE GASEOUS)

51
Q

what happens to coloured solution if pressure is increased?

A

For a coloured solution, increasing the pressure will cause it to initially go a darker color until a new equilibrium is reached

52
Q

effects of adding a catalyst on equilibrium

A

increases rate at which equilibrium is reached but has NO EFFECT ON POSITION of equilibrium (increases rate of both reverse & forward reaction equally)

53
Q

When does Kc change?

A

ONLY WITH A CHANGE IN TEMPERATURE

54
Q

effect on Kc when reaction is reversed

A

INVERT THE EXPRESSION (1/Kc)

55
Q

effect on Kc when reaction coefficients are doubled

A

SQUARE THE VALUE OF Kc –> (Kc^2)

56
Q

effect on Kc when reaction coefficients are halved

A

SQUARE ROOT THE VALUE OF Kc sqrt(Kc)

57
Q

effect on Kc when 2 reactions are added together

A

MULTIPLE THE TWO EXPRESSIONS
Kc1 x Kc2

Chemistry SL (5 decks)

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