chap3, form 5 Flashcards
definition of thermochemistry
heat change in a reaction either released or absorbed during a chemical reaction
WHAT ARE THE 2 TYPES OF HEAT CHANGE IN REACTION (so aggressive lol)
exothermic
endothermic
definition of exothermic
heat released to surrounding in the chemical reaction
gimme 3 examples of exothermic reaction
respiration
oxidation of metal
neutralisation
chemical eq of respiration bitch
C6H12O6 + 6O2 –> 6CO2 + 6H2O + heat e
chemical eq of oxidation of metal (Na)
4Na + O2 –> 2Na2O
chemical eq of neutralisation
HCl + KOH –> KCl + H2O
ΔH of exothermic is__
negative
energy change during exothermic reaction
chemical e –> heat e
definition of endothermic
heat absorbed from surrounding from the chemical reaction
gimme 3 examples of endothermic reaction
photosynthesis
decomposition of metal carbonate
decomposition of metal nitrate
chemical eq of photosynthesis
6CO2 + 6H2O –> (light on arrow) 6O2 + 6CH12O6
chemical eq of decomposition of metal carbonate
2CuCO3 –> Cu + CO2
chemical eq of decomposition of metal nitrate
2Mg(NO3)2 –> 2MgO + 4NO +O2
ΔH of endothermic is__
positive
energy change during endothermic reaction
heat e –> chemical e
definition of energy level diagram
a diagram to show energy level(heat energy content) between the reactants and the product
definition of heat of reaction, ΔH
heat is absorbed or released during a chemical reaction
unit of ΔH
kJ/mol
formula to find ΔH
Hproduct - Hreactant
describe shape of energy level diagram
straight mfs
energy level diagram: during endothermic reaction, temperature of mixture __
the total energy content of ____ is_____than “” of ____ ΔH is ___
decrease product higher reactants positive
energy level diagram: during exothermic reaction, temperature of mixture __
the total energy content of ____ is higher than “” of ____ ΔH is ___
increase product lower reactants negative
describe shape of energy profile diagram
curvy good soup
energy profile diagram: in endothermic reaction. heat energy ___ to ___ the ____ in 1 2 than heat energy ____ during ____ of bonds in ___
absorbed break bonds reactants greater released formation products
energy profile diagram: in exothermic reaction. heat energy during ___ of ___ in 1 2 than heat energy ____to ____ the bonds in ___
released formation bonds products greater absorbed break reactants
definition of activation energy
minimum energy needed to enable chemical reaction to happen
what are the 4 types of heat of reactions, ΔH
heat of: precipitation displacement neutralisation combustion
formula to find heat change/released, Q
Q = mcθ
what is density of aqueous solution and water?
1 g/cm3
what is value of specific heat capacity, c
4.2 J g-1 C-1
is heat lost to surrounding during reaction?
no
will any heat be absorbed by apparatus (thermometer)?
no
formula to find mole of solution
mol = mV/1000
formula to find mole of solid
mol = mass/molar mass
1 kJ/mol equal to __
1000 J/mol
definition of heat of precipitation
heat change when 1 mole of precipitate is formed from their Ions in an aqueous solution
thermochemical eq of heat of precipitation
cation + anion –> insoluble salt, then state ΔH+/-
unit for Q is __
Joule, J
unit for heat of reaction, ΔH
kJ/mol
heat of reaction is ___ mol
per/one
how to find heat for one mol then convert J to kJ by using mol found?
J/mol then divide by 1000
definition of heat of displacement
heat change when 1 mole of metal is displaced from its salt solution by a more electropositive metal
how many thermochemical eq for heat of displacement ?
2
name the 2 thermochemical eq for heat of displacement?
eg Fe react with CuSO4
Fe(s) + CuSO4(aq) + Cu(s) –> FeSO4(aq) + Cu(s), ΔH +/-
Fe(s) + Cu2+(aq) –> Fe2+(aq) + Cu(s), ΔH +/-
definition of heat of neutralisation
heat change when 1 mole of water is formed from the reaction between an acid an alkali
thermochemical eq for heat of neutralisation bestie
eg NaOH react with HCl
NaOH(aq) + HCl(aq) –> NaCl(aq) + H2O(l), ΔH = -57 kJ/mol
how many values of neutralisation reactions kena ingat?
4
Strong Acid + Strong Alkali
-57 kJ/mol
Weak Acid + Strong Alkali
-55 kJ/mol
Strong Acid + Weak Alkali
-52 kJ/mol
Weak Acid + Weak Alkali
-50 kJ/mol
definition of heat of combustion
heat released when 1 mole of substance is completely burnt in excess oxygen, O2
why is the value of heat of combustion always -ve?
it is an exothermic reaction
thermochemical eq of heat of combustion
eg CH4 react with O2
CH4 + 2O2 –> CO2 + 2H2O, ΔH +/-
definition of fuel value
the amount of heat energy released when one gram fuel is completely burnt in excess oxygen, O2
unit of fuel value
kJ/g
formula to find fuel value
heat combustion of substance (kJ./mol) over molar mass of substance
heat combustion is _____to no of carbons in a compound
directly proportional
so like if no of carbon ____, the heat released _____
increases
increases
application of exothermic reactions in daily life. gimme 3 and like explain shit
hot can: hot food prepared w/out external heat
termite reaction: welding of railway tracks
combustion of fuel: used for cooking food
application of endothermic reactions in daily life. gimme 3 and like explain shit
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
what are the 4 factors to consider when choosing fuel
cost, environmental effect, fuel value, availability
What is the most suitable fuel to replace petrol in vehicles and why? give like 3 reasons.
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.
Which is not the most suitable fuel to be used in vehicles? Why? 2 points and elaborate.
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.
