oceans

Question 1

what is lattice enthalpy?

Answer 1

the enthalpy change when 1 mole of solid is formed by the coming together of separate ions

Question 2

what is the main enthalpy change that prevents a substance dissolving?

Answer 2

lattice enthalpy

Question 3

what is the enthallpy change to split up an ionic compound into its ions?

Answer 3

negative lattice enthalpy

Question 4

is the enthalpy chnage to split up an ionic compound exo or endo thermic?

Answer 4

endothermic, it is positive, requires energy

Question 5

is lattice enthalpy exo or endothermic? and why?

Answer 5

exothermic as it makes ionic bonds

Question 6

what is the enthaply change of hydration?

Answer 6

the enthalpy change for the formation of 1 mole of aqueous ions from 1 mole of gaseous ions

Question 7

what bonds form between ions and molecules of water for it ti dissolve?

Answer 7

ion-diople interactions

Question 8

is ethalpy change of hydration positive or negative? and why?

Answer 8

negative as hydration is exothermic due to ion-dipole bonds made

Question 9

what effect does charge density have on the hydration enthalpy?

Answer 9

as charge density increases, there is greater attraction of water molecules so hydration enthalpy becomes more exothermic

Question 10

what effect does charge density have on lattice enthalpy?

Answer 10

as charge density increases, there is greaer electrostatic attraction between ions so lattice enthalpy becomes more negative

Question 11

what is a hydrated ion?

Answer 11

an ion with water molecules bound to them

Question 12

what is the other version of enthalpy of hydration when the solvent isnt water?

Answer 12

enthalpy of solvation

Question 13

what is the enthalpy change of solution?

Answer 13

the enthalpy change when one mole of an ionic solid becomes aqeous ionswhy

Question 14

what is the equation for enthalpy chnage of solution?

Answer 14

sum of enthalpy change of hydration - lattice enthalpy

Question 15

can a negative enthalpy change of solution dissolve?

Answer 15

yes

Question 16

why can a slightly positiive enthalpy change of solution still dissolve?

Answer 16

due to entropy

Question 17

what kind of enthalpy change of solution would occur if you dissolved an ionic compound in a non polar solvent?

Answer 17

very large positive

Question 18

what is entropy?

Answer 18

a measure of the number of ways that molecules and their associated energy (electrons) can be arranged

Question 19

what are the units of entropy?

Answer 19

JK-1mol-1

Question 20

what are 2 factors that increase the entropy of a collection of molecules?

Answer 20

the molecules spread out more

the energy is shared among more molecules

Question 21

place solid, liquid and gas in order of increasing enrpoy

Answer 21

soli liquid gas

Question 22

what would make entropy change of system positive?

Answer 22

if there are more molecules of products than reactants,

if more molecules of products are gaseous than the reactants

Question 23

what is the equation for the total entropy change for a process?

Answer 23

total entropy change = system entropy - surrounding entropy

Question 24

what is the equation for the entropy change of a system?

Answer 24

entropy of products - entropy of reactants

Question 25

what is the equation for entropy change of the surroundings?

Answer 25

entropy change of surroundings = - energy transferred/ temperature (k)

Question 26

For a spontaneous reaction what does total entropy change have to be?

Answer 26

positive

Question 27

even if total entropy change is positive, sometimes reaction does not happen, why is this?

Answer 27

activation energy is too high rate of reaction is too slow

Question 28

what is a bronsted lowrey acid?

Answer 28

a proton donator

Question 29

what is a bronsted lowrey base?

Answer 29

A proton acceptor

Question 30

what is a strong acid?

Answer 30

acids that completely disscociate in water

Question 31

how can you calculate the pH of a strong acid?

Answer 31

you know that becuase it completely dissociates, |H+| = |HA| so just use the pH=-log|H+|

Question 32

what is the equation for pH?

Answer 32

pH= -log|H+|

Question 33

What is a weak acid?

Answer 33

an acid that partially dissociates in water, the level of dissociation is measured using Ka (acid constant/ acidity constant)

Question 34

what are 2 assumptions made to calculated pH of a weak acid?

Answer 34

only a small proportion of HA dissociates to |HA| at the start = |HA| at equilibrium assume that a negligible amount of water in solution dissociates so no H+ are provided by the water so |H+| = |A-|

Question 35

What is the acid constant equation?

Answer 35

Ka = (|H+| |A-|)/|HA|

Question 36

How do you calculate the pH of a weak acid?

Answer 36

use Ka = |H+|^2 / |HA|

Question 37

What is the equation of pKa?

Answer 37

pKa= -logKa

Question 38

the lower the pKa the ________ the acid

Answer 38

stronger

Question 39

what is a strong base?

Answer 39

a base that fully dissociates in water

Question 40

what is the equation for Kw?

Answer 40

Kw= |H+| |OH-|

Question 41

How do you calculate the pH of a strong base?

Answer 41

use the Kw equation as |base|=|OH-|

Question 42

What is a buffer solution?

Answer 42

a solution of large amounts of weak acid and large amounts of the salt of this acid that will resist change in pH when small volumes of acid or alkali are added

Question 43

what happens when you add an alkali to a buffer solution?

Answer 43

it reacts with the H+ to form water so large amounts of HA dissociate to replace it equilibrium shifts to the right

Question 44

what happens if you add an acid to a buffer solution?

Answer 44

large amounts of A- react with excess H+ to make HA | equilibrium shifts to the left

Question 45

what are 2 assumptions made in buffer calculations?

Answer 45

assume all |A-| has come from the salt assume |HA| has no dissociate so |HA| a start = |HA| at equilibrium

Question 46

how do you calculate pH of buffer solution?

Answer 46

use Ka equations to find |H+| then use pH equation

Question 47

what kind of radiation from the sun reaches the earths surface?

Answer 47

UV and light

Question 48

what happens when the earth absorbs UV?

Answer 48

it heats up and radiates infrared

Question 49

green house gases in the _________ absorb _________ ___________ radiated from the ______ and ______ some of it in __ ________ this is in the _______ _________

Answer 49

troposphere infrared radiation earth reemit all directions infrared window

Question 50

how do green house gases raise the temperature of the atmosphere when they absorb infrared?

Answer 50

green house gases absorb the infrared radiation which causes their bonds to vibrate , this energy is transferred to other molecules by collision, increasing their kinetic energy and rasiing the overall temperature

Question 51

what are 3 greenhouse gases?

Answer 51

methane co2 water vapour

Question 52

what makes a green house gas contribute to the green house effect more?

Answer 52

absorbing more radiation being more abundant in the atmosphere

Question 53

what is Ksp?

Answer 53

solubility product Ksp= |A-| |B+|

Question 54

If Ksp calculated is higher than actual Ksp?

Answer 54

precipitate will form

Question 55

What factors determine the pH of a buffer solution?

Answer 55

Ka /pKa /acid strength/amount of dissociation temperature ratio/concentrations of weak acid and conjugate base/salt