Bond energy calculations GCSE Chemistry - Phoenix Hoyle | Library

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https://billvining.com/mmlib_sims/#gen_8_0

Use the simulation to visualise this.

Note 1.  In the animation the bond strength is shown by the length and the thickness of the line.

Note 2. In the products two molecules are forming so the bond energy is for two bonds.

If the energy needed to break the bonds in reactants is less than the energy released when the bonds form in the products the reaction is __________
If the energy needed to break the bonds in reactants is more than the energy released when the bonds form in the products the reaction is __________

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Reaction of nitrogen and oxygen in a car engine at high temperature and pressure to form the pollutant nitrogen oxide (this pollutant would be removed using a catalytic converter).
Bonds broken in reactants = _______ x N= + _______  x O=O
Bonds formed in products = _______ x N=O
Energy to break bonds in reactants = 1 x 945 + 1 x 498 = _______ kJ/mol
Energy to form bonds in products = 2 x 630 = _______ kJ/mol
Energy change =  energy to break bonds - energy to make bonds

Energy change = 1443 - 1260 = (sign )_______ (value) _______ 
The reaction is _______ and the temperature will _______ 

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Number of C-H bonds broken = _______ 
Number of Cl-Cl bonds broken = _______ 
Energy to break bonds = 4x413 + 243 = _______ kJ/mol
Number of C-H bonds made = _______ 
Number of C-Cl bonds made = _______ 
Number of H-Cl bonds made = _______ 
Energy given out when bonds form = 3 x 413 + 327 + 432 = _______ 
Energy change = energy in to break bonds -energy out when bonds form
Energy change =  1895 - 1998 = (sign) _______ (value) _______ kJ/mol
The reaction is _______ so the temperature of the surroundings will _______ 

1

Identify the number and type of bonds broken in the reactants
Number of C-H bonds to be broken in reactants = _______ 
Number of C-C bonds to be broken in reactants = _______ 
Number of C-O bonds to be broken in reactants = _______ 
Number of O-H bonds to be broken in reactants = _______ 

1

Calculate the number and type of bonds formed in the products.
Number of C-H bonds to be formed in products = _______ 
Number of C=C bonds to be formed in products = _______ 
Number of O-H bonds to be formed in products = _______ 

1

Calculate the energy needed to break all of the bonds in the reactants.
Total energy to break bonds = sum of 
5x C-H = 5 x 412 = _______ 
1 x C-C = 1 x 348 = _______ 
1 x C-O = 1 x 360 = _______ 
1 x O-H = 1 x 463 = _______ 
sum =  _______ kJ/mol

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Calculate the energy needed to form all of the bonds in the products.
Total energy to form bonds = sum of 
4x C-H = 5 x 412 = _______ 
1 x C=C = 1 x 612 = _______ 
2 x O-H = 2 x 463 = _______ 
sum =  _______ kJ/mol

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Energy change = energy to break bonds in reactants- energy to form bonds in products
Energy change =  _______ - _______ 
Energy change = sign _______ value _______ 
As the energy needed to break the bonds in the reactants is _______ than the energy released when the bonds form in the products the energy change is _______ and the reaction is _______ 

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Energy needed to break bonds in reactants = _______ 
Energy released to form bonds in products = _______ 
Energy change = energy to break bonds - energy to make bonds = sign _______ value _______ 

This is a combustion reaction so the temperature of the surrounding will _______ 

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Note that we often talk of temperature change of the surrounding but energy in other forms can be absorbed or released.
The electrolysis of water is ________________  . 
The energy of the products must be ____________  than the energy of the reactants. 
The formulae of the products of electrolysis are O2 and H2. 
Note in an exam I would expect the reactants and  products to be balanced.

Other Answer Choices:

endothermic

greater

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Calculate the energy change when one mole of water is electrolysed.
H-H = 436 kJ / mol
O-H = 463 kJ/mol
O=O = 496 kJ/mol

H₂O →H₂ +  ½  O₂  
Bonds broken = _______ x O-H
Bonds formed = _______ x H-H + _______ x O=O
Energy in break bonds = 2 x 463 = _______ 
Energy out in bond forming = 0.5 x 496 + 436 = _______ 
Energy change = bonds broken - bonds formed = 926-684 = (sign) _______ (value) _______ kJ/mol

What would the energy change be if one mole of hydrogen was combusted?
(sign) _______ (value) _______ kJ/mol

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Energy to break bonds in reactant = _______ 
Energy to form bonds in products = _______ 
Energy change =  energy to break bonds - energy to make bonds
Energy change = (sign) _______ (value) _______ 
This reaction is _______ as the temperature of the surroundings has _______ 

1

Energy to break bonds = _______ kJ/mol
Energy to make bonds = _______ kJ/mol
Energy change in the reaction = energy needed to break bonds - energy needed to make bonds 
Energy change in the reaction =  (sign) _______  (value) _______ kJ/mol
The energy change is _______ and the temperature of the surroundings will _______ 

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C-H bonds broken = _______ 
O=O bonds broken = _______ 
Energy needed to break bonds in reactants = _______ kJ
C-H bonds formed = _______ 
C-O bonds formed = _______ 
O-H bonds formed = _______ 
Energy given out when bonds form in the products = _______ kJ/mol
Energy change for the reaction = (sign) _______ (value) _______ kJ/mol
The reaction is _______ 
The temperature of the surroundings will _______ 

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Reaction to show oxidation of methane to form ethanol

The reaction is _______ 
The temperature of the surroundings will _______ 

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The starting temperature is _______ oC
The final temperature is _______ oC
The energy change is _______ oC
The temperature of the surroundings has _______ so the reaction is _______ 

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Enthaly change of combustion of methane = (sign) _______ (value) _______ kJ/mol

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Energy profile diagram

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Energy profile diagram

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Energy profile diagram

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Energy change and catalysts

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Energy change and catalysts

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Using ideas about bond breaking and bond formation, explain why the combustion of petrol in the petrol engine is exothermic. 
Energy absorbed to break the chemical bonds in petrol and oxygen is _________than the energy released when chemical bonds are formed in carbon dioxide and water. 
Overall, energy is _____________  into the surroundings and the temperature of the surroundings ______________  so the reaction is _______________ .