Exp 15 combined 2020

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Feb 20, 2024

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Name:_______Joshua Bultz_______________________________ Date: 11/18/20 Partner: _____________________________________ Experiment 15: the Law of Chemical Equilibrium and Le Chatelier’s Principle Pre-Lab Questions 1. For the reaction at 20ᵒC, NH 3 (aq) + H + (aq) ⇋ NH 4 + (aq), the equilibrium constant is calculated to be K = to 4.5 x10 8 . A. Write the Equilibrium expression for this reaction. Keq = [NH 4] + / [NH 4] [H+] B. From the size of the number for Keq, does the equilibrium lie to the left or to the right? Right 2. If the reaction between iron(III) ion and thiocyanate ion, Fe 3+ (aq) + SCN - (aq) ⇋ FeSCN 2+ (aq), yielded an equilibrium concentration of 0.15M for each of the two ions, what is the equilibrium concentration of the red iron(III)-thiocyanate complex ion, FeSCN 2+ ? (HINT: the equilibrium constant for the equilibrium is in the Background section in the lab manual.) Show your work . Answer only will not earn any credit! You can take a photo of your work, and insert your photo here. [FeSCN 2+] / (0.15) (0.15) 207(.15)(.15) equilibrium concentration of the red iron(III)-thiocyanate is 4.65 M 3. In the reaction below, NH 3 (g) + H 2 O (l) ⇋ NH 2 - + H 3 O + , the equilibrium constant is 10 -34 . Is this reaction likely to take place? Explain your answer. Yes, the reaction is likely. The right number of products are given. The constant does not affect the reaction.

Post-Lab Questions 1. The reaction below competes with the formation of the FeSCN 2+ complex: Fe 3+ (aq) + 4Cl - (aq) ⇋ FeCl 4 - (aq) yellow colorless Explain what would happen to the color of a dilute solution containing FeCl 4 - if a. you added a solution containing silver ion, Ag+, (silver ion reacts with chloride ion in solution to form the precipitate AgCl.) Answer: The color will be (choose one): more yellow/less yellow/the same b. you added a solution of sodium chloride, NaCl. Answer: The color will be (choose one): more yellow/ less yellow/the same c. you added concentrated HCl. Answer: The color will be (choose one): more yellow/ less yellow/the same d. you added concentrated H 2 SO 4 Answer: The color will be (choose one): more yellow/less yellow/ the same 2. The Haber process is an important reaction for the fixation of nitrogen; nitrogen is converted into ammonia, an important component in the production of fertilizers. N 2 + 3H 2 (g) ⇋ 2NH 3 (g) +22,000 cal. Consider the reaction is at equilibrium. Explain in which direction, left or right, the equilibrium is shifted when a. more nitrogen is added? Right b. more hydrogen is added? Right c. ammonia is removed? Right d. the reaction is cooled? Right

Experiment 15. The Law of Chemical Equilibrium and Le Châtelier's Principle Line 1.  What is the color of 0.1 M CuSO 4 solution? Blue  What is the co lor of the copper-ammonia complex? Dark Blue  How many drops of 1 M ammonia did you add to cause a change in color? 14 drops  Which way was the equilibrium shifted when you added ammonia? (Left/Right) Right Line 2.  How many drops of 1M HCl did you add to cause a change in color back to pale blue ? 14 drops  Which way was the equilibrium shifted when you added HCl? (Left/Right) Left Line 3.  Testing the phosphate solution, what was the color of the red li tmus paper? Got darker, a purple color.  What was the color of the blue litmus paper? A little bit purple. Line 4.  Testing the 1 M HCl solution, what was the co lor of the red litmus paper? No change.  What was the color of the blue litmus paper? Changed to red. Line 5.  After adding 1 drop of 1 M HCl to the phosphate solution and testing it with litmus paper, what was the c olor of the red litmus paper? Changed a little, slightly purple.  What was the co lo r of the blue litmus paper? Changed a little, slightly purple.  Was your phosphate so lu tion acidic, basic, or neutral A. before the addition of HCl? Base B. after the addition of HCI? Base  Which way was the equilibrium shifted when you added HCl to the phosphate solution? (Left/Right) Left

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Line 6.  Compare the colors in each of the test tubes containing the iron(III) chloride- thiocyanate mixtures: Test tube no. 1: Brownish red Test tube no. 2: Dark red Test tube no. 3: Darker Red Test tube no. 4: Orange Line 7.  In which dir ectio n did the equilibrium shift in test tube no. 2 (Left/Right) : Right test tube no. 3 (Left/Right) : Right test tube no. 4 (Left/Right) : Left Line 8.  What i s the co lor of the CoCl 2 solution a. before the addition of HCl? Pale rose b. after the addition of HCl? Dark purple  Which way was the equilibrium shifted after the addition of HCl? (Left/Right) Right Line 9.  What is the color of the CoCl 2 solution a. at room temperature? Pale rose b. at boiling water temperature? Became a little darker, pink shade. Line 10.  I n which direction did the equilibrium shif t upon heating? (Left/Right) Right Line 11.  From the above shif t , determine if the reaction was exothermic or endot hermic. Endothermic