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Investigating a factor which may (or may not) affect the value of an equilibrium constant (Kc)

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Investigating a factor which may (or may not) affect the value of an equilibrium constant (Kc) How does change in temperature affect the value of the equilibrium constant in the reaction between silver nitrate and iron (II) sulphate? Background Science: For any reversible reaction, the equilibrium constant is equal to the product of the concentrations of products divided by the product of the concentrations of the reactants. In order to calculate the equilibrium constant we will need to calculate the concentration of the products. This can be done using the formula, concentration = number of moles/ volume. Once we have established the concentration we can implement it into the formula used to calculate the equilibrium constant. The general reversible reaction is one in which w moles of A reacts with x mole of B to produce y moles of C and z moles of D therefore the general equilibrium constant equation would be: [C]y x [D]z Kc = Where Kc is the equilibrium constant [A]w x [B]x from looking at this equation it is therefore clear that by knowing the concentrations of both the reactants we can easily calculate the equilibrium constant. Due to the fact the equilibrium constant expression has the concentration of the reactants below and the concentrations of the products on top, the magnitude of the equilibrium is related to the position of the equilibrium. ...read more.


3. Catalyst Catalysts are known to affect the rate of a reaction. Due to this using a catalyst in an equilibrium reaction has the same effect on both the forward and reverse reactions in the equilibrium system. as a result there is no affect on the overall position of the equilibrium, the prescence of the catalyst only allows the system to reach the equilibrium quicker. As the catalyst does not effect the position of the equilibrium it does not effect the value of the equilibrium constant. 4. Change in temperature The effect that temperature can have on the equilibrium depends on the energy changes that take place in the chemical reaction. For exothermic reactions that are in the forward reaction, the equilibrium constant decreases with increasing temperature. However if the forward reaction is endothermic then the equilibrium increases with temperature. As we increase the temperature of a system we transfer energy to it so the equilibrium shifts to the left absorbing some of the added energy and therefore opposing the change. In a similar way when the temperature is decreased the equilibrium shifts to the right. The equilibrium I am investigating is: and I am going to be determining the affect of temperature on the value of the equilibrium constant in this reaction between Silver Nitrate and Iron(II) Sulphate. Hypothesis: The experiment taking place between the Silver Nitrate and the Iron (II) ...read more.


4. Using one of the 10 cm3 titration pipettes remove the bung and titrate 10 cm3 of solution from the conical flask trying to disturb the precipitate as little as possible and returning the bung when finished. 5. Place the titrated solution into the second clean conical flask 6. Using the second titration pipette titrate 10 cm3 of Potassium thiocyanate into the second conical flask. 7. Place a bung on top of the second conical flask. 8. Take the 400 cm3 beaker and fill it half full with water 9. Insert the bunsen burner in the gas pipe but do not turn the gas on 10. Place the gauze on top of the tripod and place the Bunsen burner underneath 11. Place the beaker of water on top of the gauze and tripod and put the thermometer in the beaker. 12. Turn on the Bunsen burner and heat the water till the temperature reaches 30oC then remove the Bunsen burner from underneath the tripod. 13. Then record the concentration of the solution 14. Continue to adjust the temperature by either adding cold water to the 400cm3 beaker of water or by adding heat using the Bunsen burner. 15. Then record the concentration of the solution in a table 16. Continue this until you have found a concentration at all your temperatures 17. Turn off all the apparatus and clear away ...read more.

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