Passage VIl Experiment 2 For each trial, students placed a known volume of a of
ID: 971303 • Letter: P
Question
Passage VIl Experiment 2 For each trial, students placed a known volume of a of thymol blue in a Citric acid (H,C,H,0) reacts with sodium hydroxide 1O M citric acid solution and a drop foam coffee cup. A lid was placed on the cup, and a ther- mometer was placed through a hole in the lid into the solu- tion. The solution's initial temperature, T,, was measured The lid was lifted, and a known volume of a 1.0 M NaOH molecules or formula units of any sub. Solution, also at T, was added to the cup. The lid was put back on the cup, and the solution was swirled. The temper- ature increased to a final (maximum) value, Te. The change (NaOH) according to the equation below. A mole is 6 x 10 stance. The equation indicates that as I mole of citric acid is consumed, 3 moles of NaOH are consumed. intemperature, , was calculated: Students red colorless aqueous solutions of citric acid and of NaOH to use in 2 experiments. The final color of the solution was also recorded (see Table 1). Table 1 Volume of Volume of citric acid NaOH solution | solution | AT | Final Trial (mL) (mL) (C) color 25 4.6 Pink 35 3.5 pink 4.6 yellow 6.1 ellow 7.2 yellow 8.0 yellow 8.4 ellow 9.0 6.8 blue 6.1 blue 2.8 blue 10 35 25 Experiment ellow blue Students placed 50 mL of a 0.1 M (0.1 mole per liter) 48 citric acid solution in a beaker. A drop of thymol blue (an acid-base indicator) was added to the solution. A measures pH was placed in the solution. Then, 30 mL of a 1.0 M NaOH solution was added to the beaker in small increments. After each addition, the solution's color and N pH were recorded (see Figure 1). Table adapted from Susan E. Hayes, The S Table adapted from Susan E. Hayes, The Stoichiometry of the Neutralization of Citric Acid: An Introductory Laboratory." 1995 by Division of Chemical Education, Inc., American Chemical Society. 14 12 10 blue solution yellow solution pink solution 10 15 volume of NaOH solution added (mL.) 20 25 30 Figure 1Explanation / Answer
35. The data which was recorded in Expt 2 but in Expt 1 is,
C. the change in temperature of solution
36. The temperature of the solution first increased and then decreases, so the graph representing this is,
H
37. Based on the equation, for every 3moles of H2O formed, 1 mole of citric acid is consumed. So for 5 molecules of H2O, ctitric acid consumed would be,
B. 2
38. Based on the color change data, the solutions would be,
soluion X solution Y
H. NaOH Citric acid
39. Based on expt. in Trial 8, the pH after addition and mixing would be,
D. greater than 8
40. In trial 2, Ti was 24 oC, do Tf would be,
J. 30.1 oC