This question is about an experiment to investigate the effect of temperature on the equilibrium constant, $$\(K_{1}\)$$, of the reaction shown. $$\[ \mathrm{Fe}^{3+}(\mathrm{aq})+\mathrm{SCN}^{-}(\mathrm{aq}) \rightleftharpoons \mathrm{FeSCN}^{2+}(\mathrm{aq}) \]$$ The data collected is used to determine the value of the enthalpy change of the reaction. To set up the equilibrium, aqueous iron(III) nitrate, $$\(\mathrm{Fe}\left(\mathrm{NO}_{3}\right)_{3}(\mathrm{aq})\)$$, is mixed with aqueous potassium thiocyanate, $$\(\mathrm{KSCN}(\mathrm{aq})\)$$. Aqueous iron thiocyanate ions, $$\(\operatorname{FeSCN}^{2+}(\mathrm{aq})\)$$, have a red colour. A colorimeter is used to measure the absorbance of the reaction mixture. A calibration graph can then be used to determine the concentration of $$\(\mathrm{FeSCN}^{2+}(\mathrm{aq})\)$$ in the reaction mixture. Table 2.1 shows the solutions for the experiments. The following experimental procedure is used. step 1 Half-fill a large beaker with water at room temperature $$\(\left(25^{\circ} \mathrm{C}\right)\)$$. step 2 Transfer about $$\(40 \mathrm{~cm}^{3}\)$$ of solution B into a boiling tube and place the boiling tube in the beaker of water. step 3 Transfer $$\(5.00 \mathrm{~cm}^{3}\)$$ of solution $$\(\mathbf{C}\)$$ into a test-tube and place the test-tube in the beaker of water. step 4 Wait for 10 minutes. step 5 Transfer $$\(5.00 \mathrm{~cm}^{3}\)$$ of solution B from the boiling tube to the test-tube containing solution C. Stir the mixture in the test-tube and record the temperature of the mixture. step 6 Measure the absorbance of the mixture in the test-tube using the colorimeter. Change the temperature of the water in the beaker and repeat steps 3 to 6 for different temperatures. (i) Identify the dependent variable. ................................................................................................................................. (ii) Describe how you would adjust the temperature of the water in the large beaker to obtain a temperature of $$\(10^{\circ} \mathrm{C}\)$$. .................................................................................................................................

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