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unit 2 Flashcards

1
Q

why define enthalpy change

A

the heat energy that is transfered between the system and the surroundings at a constant pressure

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2
Q

define standard enthalpy chnage of combustion

A

the enthalpy change measured at 100kPa and a specific temp when 1 mol of a substance is completely used up

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3
Q

give 3 sources of error in of combustion process

A

some of the energy rpoduced in burnign in sent to the air and not the water

incomplete combustion of ethanol

some of the heat energy is sent to the copper can and not to the water

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4
Q

defien standard enthaly change of neutralisation

A

the enthalpy change mesured at 100kpa and a specified temp when 1 mol of water is prodced by the neutralisation of an acid with an alkali

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5
Q

define standard enthalpy change of formation

A

the enthalppy chnange meausred at 100kpa and a specific temp when 1 ol of a substance is formed from its elements in their standard sates

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6
Q

why r london fores considered non polar

A

cuz the elctron density is symetricly distributed thruout the molecule

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7
Q

wt r the 2 reasons for the increase in boiling temp with increasing molecular mass

A

as molecular mass incrades, the no of electrons per molecule increase so the indued dipoles also increases

at the length of the carbon chain increases, the no of points of contact between adjacent molecules increases, which increases dipole infused dipole forces cu zof the contact so more london forces.

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8
Q

define enthalpy chnage if vapourisation

A

amount of energy needed to copletely seperate the molecules of a liquid and convert it into a gas at the same temp

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9
Q

the hydrogen bond strenght for hydrogen fluiride i greater than the hydrogen bond stregnth for H20 but tis boiling temp is lower….why

A

cuz HF forms 2 hydrogen bonds per molecule while water molecules can form up to four hydrogen bonds per molecule.

not all the the hydrogen bonds in HF is broken on vapouritsation, since HF is polymerised, even in the gas phase

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10
Q

wt r the 2 ocnditions that shud be met for a substance to dissolve

A

the solute particles shud be seperated from each other and then become surrounded by solvent particles

the forces of attraction between the solute and solvent particles shud be strong enough to overcome the solvent-solvent forces and solute-solute forces

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11
Q

why cant non polar molecules like alkanes dissolve in water

A

cus the attraction between the alknaane molecules nd water molecules isnt strong enough to break the hydrogen bonded system breween the water molecules.

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12
Q

define first ionisation energy

A

the energy needed to remove an electron rom each atom in 1mol of atoms in the gaseous state

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13
Q

define second ionisation energy

A

the eneryg needed to remove an electron from each singly charged ion in 1mol fo postive ions in the gaseous state

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14
Q

wt happens when magnesium is burnt in air

A

bright flame and formation of a white solid

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15
Q

wt is milk of magnesia made of

A

a saturated solution of magnesium hydroxide mixed with extra solid magnesium hydroxide which acts as an antacid

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16
Q

describe the test for sulfate ions

A

first add dilute hydrochloric acid to the solution to remove any carbonate ions that could interfere. Then add barium chloride (BaCl₂) solution. A white precipitate of barium sulfate (BaSO₄) indicates the presence of sulfate ions

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17
Q

how is the colour from the flame test produced

A

the electrons move to a higher energy leel to an excited state. the electron then returns to its ground state which releases energy, this produced coour

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18
Q

wt is the test for ammonium ions

A

add NaOH and warm the mix ths wud release ammonia gas. use a damp litmus paper, it wud turn blue to confirm the presence

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19
Q

how is an instantaneous dipole created between two halogens

A

as the two atoms in the diatomic moluecles r identical, the pair of electrons forming the covalent bond between them is shared equaloly. this means that halogen molecules r non polr, but as the postivie charges of the protons in the two nuclei r in fixed positions, the electron desntiy in a halogen molecule fluctuates. this reuslts in a instantenous dipole

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20
Q

wt happens when u add conc sulfuric acid to NaCI

A

misty fumes

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21
Q

wt happens when u add conc sulfuric acid to NaBr

A

misty fumes
brown fumes
colourless gas and chocking smell

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22
Q

wt happens when u add conc sulfuric acid to NaI

A

misty fumes
purple fumes
yellow solid
rotten egg smell

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23
Q

name 3 primary standards of a standard solution

A

they shud be solids with high molar masses
they shud be chemically stable
they shud be soluble in water

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24
Q

wts methyl organe cooour in acid

A

red

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25
define mistakes
human errors due to incorrect procedures, misreading measurements, or calculation errors.
26
define errors and describe the two types
These are uncertainties in measurements and can be categorized as: Systematic errors: error caused by apparuts and leads to the recorded value being too low or high Random errors: error caused by unpredictalble changes in conditions like temp or pressure
27
systemsic errors 2 exs
faulty equipments wrong calbration
28
random errors 2 exs
fluctuations in temperature, inconsistent readings
29
define accuracy
how close a measured value is to the true or accepted value.
30
define precision
how close repeated measurements are to each other
31
rate of reaction equation
change in conc/time for change to happen
32
wt r the 2 requirementes for a reaction to occur
the two moleculres shud collide with enoiugh energy to caue a reaction the two molecules shud collide in the corret orientation
33
wt is activation energy
the min energy that colllidng particles shud hve for a reation to occur
34
describe the effect on increasing conc of the rate of reaction
it increases rate, as the frequency of succrssful collisions between reacting solute particles also increases. this is cuz they r clooser together
35
describe the effect of increasing pressure on the rate of reaction in a gas phase
if the pressure of thre gas is increased, there will be more reactant molecules ina given voume of mixture, the frequency of collisions will increase which icnreases the rate of reaction
36
describe the effect of changing pressure on the rate of rraction in solid or liquid phase
no effet cuz the volume of solids and liquids changes vert little when they r put under pressure so their particles dont move closer together
37
describe the effet of increasing surface area on the rate of reaction
-it speeds up the reaction because more particles are exposed, leading to a higher frequency of successful collisions between reactant molecules. According to collision theory, reactions occur when particles collide with enough energy, so a greater surface area allows more frequent and effective collisions, increasing the reaction rate.
38
2 economic advantages of using catalysts
they increase the rate of a chem reaction so more of the desired product can be mde in the desired time period reaction can take place at lower temps reuslting in teh energy costs to the manufactoruee
39
why is the reactin between hydrogen and iodoie considered reversible
cuz if a sample of hydrogen iodide is heated to 573K in a closed system , it partialy decomposes. the mixture formed is identical to that produced when starting with an equimolar mixture of hydrogen and iodine. the reaction is reversible and when there is no further change in the conc of the reactants and produts, the system is in equilibrium
40
wt r the two conditions that shud be there for dynamic equilibrium to be established
the reaction shud be reversible the reaction mixture must be in a closed container
41
wt r the 3 important features that define a system is in equilibrium
both forward and backwards reaction r continously happening rate of forward reaction is equal to the rate of backward reaction the conc of reactrants and produts r constant
42
wt r the 4 factors that may affect the posiotn of equilibrium of a reaction mix
conc of a component pressure of a system temp of the system addition of a catalyst
43
wt is the effect of increasing conc in equilibrium
if the conc is increased, the rate of the forward reaction will increase and more products will form. as the conc of the products increase, the rate of the backward reaction increases and a new equilibrium is made. equilibrium moves to the right, with more produts being present than the original position
44
wt happens to the equilibirum if the conc of the reactants is decreased
the position of equilibrium moves to the left to prododuce more reactants
45
wt happens to the equiblrium is pressure is increased
the equilibirum tries to reudce the pressure by moving to the side with less molecules so it moves to the right
46
wt happens to the equilibrium if the temp is increased
equilibrium treies to decrease the temp by absoring ehat so endothermic reaction is formed. equilibrium position moves to the left
47
describe the effect of adding a catalyst in equilibrium
if a catalyst is added to a reaction micture that is in equilibrium, the rate of forward and backward reactions will increase. the increase in rate will be the same for both reaction so the position of equilibrium isnt altered
48
wt happens to the maxwell boltzman distribution curve when the temp is increased
the particles hve higher kintetic energy. a larger amount of molecules hve higher energy than ativation energy. as the temp increases, the peak height decreases and moves to the right.
49
how does a catalyst decrease activation energy
A catalyst lowers activation energy by providing an alternative reaction pathway with a lower energy barrier, allowing more reactant molecules to collide successfully and react. It does this by stabilizing the transition state
50
name the process that is used to manufacture ammonia and describe it and profivde the equartion
its called the haber process. its manufactured by directed syntheisis from nitrogen and hydrogen N2(g) + 3H2(g) ⇌ 2NH3(g) ΔH= +92 kJ/mol the conditions r 450.C and 250atm, uses iron catalyst
51
name the process that is used to manufacture sulfuric acid and describe it and profivde the equartion
its called the contact process reaction between sulfur dioxide and oxygen at the surface of a solid vanadium(V) oxide, V2O5 catalyst to form sulfur trioxide SO2(g) + ½O2(g) ⇌ SO3(g) ΔH= -96 kJ/mol the conditions r 450.C and 1 atm
52
how to find the rate of hydrolysis of halogens
use ehtanol as a solvent for the mixture. controle variables like temp, conc and quantity of halogenoalkanes. time the appearence of the precipitate
53
describe a method of making alcohols wit a halogenoalkane and provide equation for an exmaple
heating a halogenoalkane with aq potassium hydroxide under reflux. ex - conversion of 1-chloroprpane into propan-1-ol CH3CH2CH2CL + KOH ---> CH3CH2CH2OH + KCI
54
describe a method of making nitriles with a halogenoalkane
heating a halogenoalkane with potassium cyanide dissovled in ethanol under a reflux
55
describe a method of making primary amines
heating a halogenoalkane with amonnia solution under pressure in a sealed tube
56
wt is formed when a secondary alcohol is oxidesed
a ketone
57
wt is the product formed when a primary alcohol is oxidised
aldehyde
58
wt is formed when an aldehyde is oxidsed
a carboxylic acid
59
in complete oxidation of alcohols to get a ketone and carboxylic acid, wt technique can be used
heating under reflux
60
in incomplete oxidation of alcohols to get an aldehyde and not a carboxylic acid wt technique can be used
distillation with addition
61

Chemistry (4 decks)

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