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Physical chemistry - Coggle Diagram

- - - - neutralisation
      - combustion
- - - - NH3 (g) + HCl (g) → NH4Cl (s)
        
        As hot gases cool down they recombine to form solid ammonium chloride
      - NH4Cl (s) ⇌ NH3 (g) + HCl (g)
        
        This means it is a reversible reaction
      - NH4Cl (s) → NH3 (g) + HCl (g)
        
        Heting up ammonium chloride produces ammonia and hydrogen chloride gases
    - - An example of this is hydrated copper(II) sulfate ⇌ anhydrous copper(II) sulfate + water
      - https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=1080/https://cdn.savemyexams.com/uploads/2021/07/6.2.2-Energy-Changes-_-Reversible-Reactions.png
      - hydrated salts of copper sulfate are normaly blue
        
        hydrated salts can be heated to form an anahydrate solution in an endothermic reaction
      - anahydrous salts of copper sulfate are white
        
        Adding water to an anahydrous salt can be used to form hydrated salts in a exothermic reaction
- - - - Enthalpy changes of reactions in solution
        
        To calculate the amount of energy produced by a chemical reaction in solution we measure the temperature change when the solutions are mixed together
        
        To measure enthalpy change the solutions must be mixed in an insulated enviroment
        
        How to carry out the experiment
        
        For the purposes of the calculation assumptions are made of the experiment
        
        heat capacity of the container is ignored
        
        the reaction is complete
        
        The density of the solution is the same as water
        
        the heat capacity is asumed to be 4.18J/g/ºC (same as water)
        
        A calorimeter can be made up of a polystyrene drinking cup, a vacuum flask or metal can
        
        Method
        
        An excess amount of the second reagent is added and the solution is stirred continuously
        
        The maximum temperature is recorded and the temperature rise calculated
        
        1.A fixed volume of one reagent is added to the calorimeter and the initial temperature taken with a thermometer
        
        https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=1920/https://cdn.savemyexams.com/uploads/2024/08/18446_1-5-chemical-energetics-calorime.png
        
        Calculating enthalpy change
        
        Q = m x c x ΔT
        
        m= the massof the substance being heated (g)
        
        c=the specific heat capacity (J/g/ºC) The specific heat capacity of water is 4.18
        
        Heat capacity is the energy needed to raise the temperature of 1g of substance by 1 ºC
        
        Q=the heat energy change J
        
        ΔT=the temperature change ºC
      - Enthalpy changes of combustion
        
        The principle here is to use the heat released by a combustion reaction to increase the heat content of water
        
        calomitery experiment
        
        https://cdn.savemyexams.com/cdn-cgi/image/f=auto,width=1920/https://cdn.savemyexams.com/uploads/2024/08/50507_5-1-4-simple-calorimeter-1.png
        
        method
        
        Measure a fixed volume of water into a copper can
        
        Weigh the spirit burner containing a fuel using a balance
        
        Measure the initial temperature of the water
        
        Burn the fuel and stir the water
        
        Wait until the temperature has risen by approximately 20 oC and extinguish the flame
        
        Record the final temperature of the water and re-weigh the spirit burner