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chemistry > chap3, form 5 > Flashcards

chap3, form 5 Flashcards

1
Q

definition of thermochemistry

A

heat change in a reaction either released or absorbed during a chemical reaction

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2
Q

WHAT ARE THE 2 TYPES OF HEAT CHANGE IN REACTION (so aggressive lol)

A

exothermic

endothermic

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3
Q

definition of exothermic

A

heat released to surrounding in the chemical reaction

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4
Q

gimme 3 examples of exothermic reaction

A

respiration
oxidation of metal
neutralisation

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5
Q

chemical eq of respiration bitch

A

C6H12O6 + 6O2 –> 6CO2 + 6H2O + heat e

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6
Q

chemical eq of oxidation of metal (Na)

A

4Na + O2 –> 2Na2O

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7
Q

chemical eq of neutralisation

A

HCl + KOH –> KCl + H2O

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8
Q

ΔH of exothermic is__

A

negative

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9
Q

energy change during exothermic reaction

A

chemical e –> heat e

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10
Q

definition of endothermic

A

heat absorbed from surrounding from the chemical reaction

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11
Q

gimme 3 examples of endothermic reaction

A

photosynthesis
decomposition of metal carbonate
decomposition of metal nitrate

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12
Q

chemical eq of photosynthesis

A

6CO2 + 6H2O –> (light on arrow) 6O2 + 6CH12O6

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13
Q

chemical eq of decomposition of metal carbonate

A

2CuCO3 –> Cu + CO2

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14
Q

chemical eq of decomposition of metal nitrate

A

2Mg(NO3)2 –> 2MgO + 4NO +O2

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15
Q

ΔH of endothermic is__

A

positive

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16
Q

energy change during endothermic reaction

A

heat e –> chemical e

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17
Q

definition of energy level diagram

A

a diagram to show energy level(heat energy content) between the reactants and the product

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18
Q

definition of heat of reaction, ΔH

A

heat is absorbed or released during a chemical reaction

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19
Q

unit of ΔH

A

kJ/mol

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20
Q

formula to find ΔH

A

Hproduct - Hreactant

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21
Q

describe shape of energy level diagram

A

straight mfs

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22
Q

energy level diagram: during endothermic reaction, temperature of mixture __
the total energy content of ____ is_____than “” of ____ ΔH is ___

A 
decrease
product
higher 
reactants
positive
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23
Q

energy level diagram: during exothermic reaction, temperature of mixture __
the total energy content of ____ is higher than “” of ____ ΔH is ___

A 
increase
product 
lower
reactants
negative
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24
Q

describe shape of energy profile diagram

A

curvy good soup

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25
Q

energy profile diagram: in endothermic reaction. heat energy ___ to ___ the ____ in 1 2 than heat energy ____ during ____ of bonds in ___

A 
absorbed
break
bonds
reactants
greater
released
formation
products
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26
Q

energy profile diagram: in exothermic reaction. heat energy during ___ of ___ in 1 2 than heat energy ____to ____ the bonds in ___

A 
released
formation 
bonds
products
greater
absorbed
break 
reactants
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27
Q

definition of activation energy

A

minimum energy needed to enable chemical reaction to happen

28
Q

what are the 4 types of heat of reactions, ΔH

A 
heat of:
precipitation
displacement
neutralisation
combustion
29
Q

formula to find heat change/released, Q

A

Q = mcθ

30
Q

what is density of aqueous solution and water?

A

1 g/cm3

31
Q

what is value of specific heat capacity, c

A

4.2 J g-1 C-1

32
Q

is heat lost to surrounding during reaction?

A

no

33
Q

will any heat be absorbed by apparatus (thermometer)?

A

no

34
Q

formula to find mole of solution

A

mol = mV/1000

35
Q

formula to find mole of solid

A

mol = mass/molar mass

36
Q

1 kJ/mol equal to __

A

1000 J/mol

37
Q

definition of heat of precipitation

A

heat change when 1 mole of precipitate is formed from their Ions in an aqueous solution

38
Q

thermochemical eq of heat of precipitation

A

cation + anion –> insoluble salt, then state ΔH+/-

39
Q

unit for Q is __

A

Joule, J

40
Q

unit for heat of reaction, ΔH

A

kJ/mol

41
Q

heat of reaction is ___ mol

A

per/one

42
Q

how to find heat for one mol then convert J to kJ by using mol found?

A

J/mol then divide by 1000

43
Q

definition of heat of displacement

A

heat change when 1 mole of metal is displaced from its salt solution by a more electropositive metal

44
Q

how many thermochemical eq for heat of displacement ?

A

2

45
Q

name the 2 thermochemical eq for heat of displacement?

eg Fe react with CuSO4

A

Fe(s) + CuSO4(aq) + Cu(s) –> FeSO4(aq) + Cu(s), ΔH +/-

Fe(s) + Cu2+(aq) –> Fe2+(aq) + Cu(s), ΔH +/-

46
Q

definition of heat of neutralisation

A

heat change when 1 mole of water is formed from the reaction between an acid an alkali

47
Q

thermochemical eq for heat of neutralisation bestie

eg NaOH react with HCl

A

NaOH(aq) + HCl(aq) –> NaCl(aq) + H2O(l), ΔH = -57 kJ/mol

48
Q

how many values of neutralisation reactions kena ingat?

A

4

49
Q

Strong Acid + Strong Alkali

A

-57 kJ/mol

50
Q

Weak Acid + Strong Alkali

A

-55 kJ/mol

51
Q

Strong Acid + Weak Alkali

A

-52 kJ/mol

52
Q

Weak Acid + Weak Alkali

A

-50 kJ/mol

53
Q

definition of heat of combustion

A

heat released when 1 mole of substance is completely burnt in excess oxygen, O2

54
Q

why is the value of heat of combustion always -ve?

A

it is an exothermic reaction

55
Q

thermochemical eq of heat of combustion

eg CH4 react with O2

A

CH4 + 2O2 –> CO2 + 2H2O, ΔH +/-

56
Q

definition of fuel value

A

the amount of heat energy released when one gram fuel is completely burnt in excess oxygen, O2

57
Q

unit of fuel value

A

kJ/g

58
Q

formula to find fuel value

A

heat combustion of substance (kJ./mol) over molar mass of substance

59
Q

heat combustion is _____to no of carbons in a compound

A

directly proportional

60
Q

so like if no of carbon ____, the heat released _____

A

increases

increases

61
Q

application of exothermic reactions in daily life. gimme 3 and like explain shit

A

hot can: hot food prepared w/out external heat

termite reaction: welding of railway tracks

combustion of fuel: used for cooking food

62
Q

application of endothermic reactions in daily life. gimme 3 and like explain shit

A

gel pads: relieve fever by absorbing heat from body

self cooling beverages: drinks in cold cans, kept cool with tin acting as insulator to not absorb external heat

sorbet: tongue feels cool when sorbet is put in moth

63
Q

what are the 4 factors to consider when choosing fuel

A

cost, environmental effect, fuel value, availability

64
Q

What is the most suitable fuel to replace petrol in vehicles and why? give like 3 reasons.

A

Ethanol. As it doesn’t produce soot, it is environmentally friendly. Secondly, it is flammable thus burns easily. Thirdly, it burns with blue flame, meaning lots of heat energy is produced.

65
Q

Which is not the most suitable fuel to be used in vehicles? Why? 2 points and elaborate.

A

Hydrogen gas. It is an explosive gas. If not handled properly it will cause an explosion. The procedure to prepare hydrogen gas is expensive, which is fractional distillation.

chemistry (8 decks)

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