Passage
Living organisms that require oxygen to respire can build up hydrogen peroxide (H₂O₂) as a byproduct of respiration. Because hydrogen peroxide can cause oxidative damage to cells, the amount of H₂O₂ in cells must be closely regulated. Although H₂O₂ decomposes spontaneously, a catalyst is needed for the reaction to occur at a sufficiently rapid rate suitable for biological purposes. In biological systems, an enzyme called a catalase accelerates the catalytic decomposition of H₂O₂ into water and oxygen (Reaction 1) .
Reaction 1In a laboratory setting, several different inorganic compounds can also serve as catalysts for H₂O₂ decomposition, allowing researchers to compare how different catalysts affect the efficiency of the reaction. To compare Fe(NO₃) ₃ (a metal homogeneous catalyst) and NaI (a halogen homogeneous catalyst) , researchers measured the amount of heat evolved after placing each catalyst in a fresh solution of 3% hydrogen peroxide.To perform the measurements, the researchers placed 50 mL of 3% H₂O₂ in an insulated coffee cup to be used as a calorimeter, as shown in Figure 1. Before adding any catalyst, the initial, baseline temperature of the H₂O₂ solution was determined by recording the temperature every 30 seconds for 5 minutes. Then 10 mL of 0.10 M Fe(NO₃) ₃(aq) catalyst was added to the H₂O₂ solution. The temperature was recorded every 30 seconds for another 15 minutes. The experiment was then repeated using 10 mL of 0.50 M sodium iodide in 0.01 M NaOH as the catalyst. The results for each reaction are shown in Figure 2.
Figure 1 Coffee cup calorimeter
Figure 2 Temperature vs. time measurements for reactions catalyzed by Fe(NO₃) ₃ and NaI
Adapted from: C. Marzzacco, "The effect of a change in catalyst on the enthalpy of decomposition of hydrogen peroxide." Chem13 News Magazine. ©2008 University of Waterloo.
-Based on the results in Figure 2, the magnitude of ΔT for the decomposition of H₂O₂ using Fe(NO₃) ₃ is closest to which of the following?

Question

Passage
Living organisms that require oxygen to respire can build up hydrogen peroxide (H₂O₂) as a byproduct of respiration. Because hydrogen peroxide can cause oxidative damage to cells, the amount of H₂O₂ in cells must be closely regulated. Although H₂O₂ decomposes spontaneously, a catalyst is needed for the reaction to occur at a sufficiently rapid rate suitable for biological purposes. In biological systems, an enzyme called a catalase accelerates the catalytic decomposition of H₂O₂ into water and oxygen (Reaction 1) .

Passage Living organisms that require oxygen to respire can build up hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) as a byproduct of respiration. Because hydrogen peroxide can cause oxidative damage to cells, the amount of H<sub>2</sub>O<sub>2</sub> in cells must be closely regulated. Although H<sub>2</sub>O<sub>2</sub> decomposes spontaneously, a catalyst is needed for the reaction to occur at a sufficiently rapid rate suitable for biological purposes. In biological systems, an enzyme called a catalase accelerates the catalytic decomposition of H<sub>2</sub>O<sub>2</sub> into water and oxygen (Reaction 1) . <strong>Reaction 1</strong>In a laboratory setting, several different inorganic compounds can also serve as catalysts for H<sub>2</sub>O<sub>2</sub> decomposition, allowing researchers to compare how different catalysts affect the efficiency of the reaction. To compare Fe(NO<sub>3</sub>) <sub>3</sub> (a metal homogeneous catalyst) and NaI (a halogen homogeneous catalyst) , researchers measured the amount of heat evolved after placing each catalyst in a fresh solution of 3% hydrogen peroxide.To perform the measurements, the researchers placed 50 mL of 3% H<sub>2</sub>O<sub>2</sub> in an insulated coffee cup to be used as a calorimeter, as shown in Figure 1. Before adding any catalyst, the initial, baseline temperature of the H<sub>2</sub>O<sub>2</sub> solution was determined by recording the temperature every 30 seconds for 5 minutes. Then 10 mL of 0.10 M Fe(NO<sub>3</sub>) <sub>3</sub>(aq) catalyst was added to the H<sub>2</sub>O<sub>2</sub> solution. The temperature was recorded every 30 seconds for another 15 minutes. The experiment was then repeated using 10 mL of 0.50 M sodium iodide in 0.01 M NaOH as the catalyst. The results for each reaction are shown in Figure 2. <strong>Figure 1</strong> Coffee cup calorimeter <strong>Figure 2</strong> Temperature vs. time measurements for reactions catalyzed by Fe(NO<sub>3</sub>) <sub>3</sub> and NaI Adapted from: C. Marzzacco, The effect of a change in catalyst on the enthalpy of decomposition of hydrogen peroxide. Chem13 News Magazine. ©2008 University of Waterloo. -Based on the results in Figure 2, the magnitude of ΔT for the decomposition of H<sub>2</sub>O<sub>2</sub> using Fe(NO<sub>3</sub>) <sub>3</sub> is closest to which of the following? A) −11 °C B) 10 °C C) 23 °C D) 33 °C

Reaction 1In a laboratory setting, several different inorganic compounds can also serve as catalysts for H₂O₂ decomposition, allowing researchers to compare how different catalysts affect the efficiency of the reaction. To compare Fe(NO₃) ₃ (a metal homogeneous catalyst) and NaI (a halogen homogeneous catalyst) , researchers measured the amount of heat evolved after placing each catalyst in a fresh solution of 3% hydrogen peroxide.To perform the measurements, the researchers placed 50 mL of 3% H₂O₂ in an insulated coffee cup to be used as a calorimeter, as shown in Figure 1. Before adding any catalyst, the initial, baseline temperature of the H₂O₂ solution was determined by recording the temperature every 30 seconds for 5 minutes. Then 10 mL of 0.10 M Fe(NO₃) ₃(aq) catalyst was added to the H₂O₂ solution. The temperature was recorded every 30 seconds for another 15 minutes. The experiment was then repeated using 10 mL of 0.50 M sodium iodide in 0.01 M NaOH as the catalyst. The results for each reaction are shown in Figure 2.

Figure 1 Coffee cup calorimeter

Figure 2 Temperature vs. time measurements for reactions catalyzed by Fe(NO₃) ₃ and NaI
Adapted from: C. Marzzacco, "The effect of a change in catalyst on the enthalpy of decomposition of hydrogen peroxide." Chem13 News Magazine. ©2008 University of Waterloo.
-Based on the results in Figure 2, the magnitude of ΔT for the decomposition of H₂O₂ using Fe(NO₃) ₃ is closest to which of the following?

Quizplus · Accepted Answer

11ecba2d_1218_7576_a3bf_7b7afe518454_MD0008_00 A calorimetry experiment measures the temperature T as a reaction progresses. The results are displayed graphically with temperature (the dependent variable) on the y-axis and time (the independent variable) on the x-axis. Any change in temperature ΔT caused by heat that is either released or absorbed during the reaction is seen as a sharp increase or decrease along the y-axis. The magnitude of ΔT is found by subtracting the initial temperature T_i at the beginning of the reaction from the final temperature T_f at the end of the reaction. 11ecba2d_1218_9c87_a3bf_1f5df94d0eb6_MD0008_00 Although T_f and T_i are usually evaluated using trend lines, ΔT can often be reasonably estimated by using temperatures immediately before and after the sharp vertical change in the graph as the values of T_f and T_i. The experiment described in the passage observed an increase in temperature caused by the heat evolved from the catalytic decomposition of H₂O₂. The approximate ΔT for the reaction can be found by evaluating T_f and T_i. Figure 2 shows that the temperature at the beginning of the reaction (T_i) is 23 °C. According to Reaction 1, heat is one of the products of the reaction; therefore, when the reaction stops producing heat (ie, the temperature stops rising), the reaction ends. On this basis, the temperature at the end of the reaction (T_f) is approximately 33 °C. Substituting these values of T_f and T_i into the equation above gives 11ecba2d_1218_9c88_a3bf_899b6091242a_MD0008_00 11ecba2d_1218_9c89_a3bf_c1799e226968_MD0008_00 (Choice A) A temperature of −11°C is found if the NaI reaction is evaluated instead of the Fe(NO₃)₃ reaction and the T_i and T_f are switched. This is incorrect because heat is released from the reaction, making T_f higher than T_i; therefore, ΔT should be positive. (Choices C and D) Temperatures of 23°C and 33°C are the approximate initial and final temperatures, respectively, rather than the change in temperature. Educational objective: Calorimetry experiments measure the temperature as a reaction progresses. Any change in temperature ΔT during the reaction is found by subtracting the initial temperature T_i at the beginning of the reaction from the final temperature T_f at the end of the reaction.

Passage Living Organisms That Require Oxygen to Respire Can Build Up