(A3) Energy Changes in Industry Flashcards
Celsius to Kelvin
°C + 273 = K
What is standard condition?
The condition of the environment need for experiments
Standard Condition (Room Temperature)
298K
Standard Condition (Pressure)
100 Kpa or 1 atm
What is activation energy?
Activation energy is the minimum amount of energy required by reactants to form products
What happens in the reaction profile of an exothermic reaction?
The energy of the products is lower than the energy of the reactants because energy is released
What happens in the reaction profile of an endothermic reaction?
The energy of the products is higher than the energy of the reactants because energy is be taken in
What is exothermic?
Bond making
What is endothermic?
Bond breaking
Is the enthalpy of an endothermic reaction positive or negative?
Positive
Is the enthalpy of an exothermic reaction positive or negative?
Negative
Why is the enthalpy of an exothermic reaction positive?
Energy is released from the reaction when a bond is made
Why is the enthalpy of an endothermic reaction postive?
Where energy is taken in from the surroundings to break a bond
What is the system?
Where the reaction is occurring
What is the surroundings?
Where the energy of the reaction can transfer to?
What halogens are a gas?
F₂ and CL₂
What halogens are a liquid?
Br₂
What halogens are a solid?
I₂
What is enthalpy?
The thermal energy stored in a chemical system
How can enthalpy be measured?
If the temperature of a reaction has changed
Enthalpy Change Equations
Enthalpy Change = Enthalpy taken in - enthalpy taken out
Enthalpy Change = Enthalpy to break bonds - Enthalpy to make bonds
Enthalpy Change = Enthalpy of reactants - Enthalpy of products
What is necessary for any reaction to happen
Bonds must be broken in reactants
Bonds must be made in products
Enthalpy Equation
H = U + PV
What happens to the enthalpy as we go down a group?
The reaction becomes less exothermic
Why does the reaction get less exothermic as we go down a group?
Because the size of the ion gets bigger so less energy is released when bonds forms
What happens to the enthalpy when the charge of the metal ion increases?
The reaction becomes more exothermic
Why does the reaction get more exothermic as the charge of the metal ion increases?
Because the metal ion gets smaller due to the increased charge.
The increased charge causes the attraction to become stronger and more energy is released when bonds form.
What happens to the enthalpy as we go across a period?
- The charge of the ion increases, attraction becomes stronger so the ion becomes smaller
- The reaction become more exothermic so more energy so released when bonds are formed
What is the enthalpy of formation?
Enthalpy change when one mole of a substance is formed from all its elements in its standard state
Example equation of enthalpy of formation
2 Na (s) + ¹/²O₂(g) –> Na₂O (s)
What is the enthalpy of combustion?
Enthalpy change when one mole of a substance undergoes complete combustion with all its substances in their standard state
Example equation of enthalpy of combustion
H₂ (g) + ¹/²O₂(g) –> H₂O (l)
What is the enthalpy of hydration?
Enthalpy change when one mole of gaseous ions become hydrated
Example equation of enthalpy of hydration
Mg²⁺ (g) + aq –> Mg²⁺ (aq)
