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Monday, Nov. 4 th : “A” Day Tuesday, Nov. 5 th : “B” Day Agenda

Monday, Nov. 4 th : “A” Day Tuesday, Nov. 5 th : “B” Day Agenda. Check lab write-ups Lab Discussion/Safety Items Conduct lab and begin calculations: “ Calorimetry and Hess’s Law” Homework: Concept Review We will finish the lab calculations next time and the lab will be due….

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Monday, Nov. 4 th : “A” Day Tuesday, Nov. 5 th : “B” Day Agenda

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  1. Monday, Nov. 4th: “A” Day Tuesday, Nov. 5th: “B” DayAgenda • Check lab write-ups • Lab Discussion/Safety Items • Conduct lab and begin calculations: “Calorimetry and Hess’s Law” • Homework: Concept Review • We will finish the lab calculations next time and the lab will be due…

  2. “Calorimetry and Hess’s Law”Discussion • There are 3 different reactions you will be running, all using hydrochloric acid (HCl) and sodium hydroxide (NaOH). • Be sure to CLOSE the NaOH container when done using it because it is hygroscopic, meaning it will absorb moisture from the air and gain mass. • Make sure to use the glass beaker inside the metal calorimeter – DO NOT pour the acids and bases directly into the metal calorimeter – they are corrosive and will damage (pit) the calorimeter!

  3. “Calorimetry and Hess’s Law” Safety Issues • You do not have to wear gloves when handling the NaOH, but you must use the porcelain scoop. Do not touch the pellets! • HCl is hydrochloric acid – be careful when handling it. • Make sure you are using the correct solution; there are 3 different solutions used in this lab. READ THE LABELS!

  4. “Calorimetry and Hess’s Law” • Rinse off the thermometer probe and stirring rod thoroughly with distilled water each time after recording the temperatures. DO NOT touch the metal probe until it’s been rinsed off. • The actual laboratory part of this lab is not difficult, it’s the calculations that will take some time. • We will go through the calculations together back in the classroom…

  5. “Calorimetry and Hess’s Law” • In the Analysis section: you need to complete #1-#4 TODAY! • Follow all directions carefully and have

  6. Lab: “Calorimetry and Hess’s Law” Analysis 1. Organizing Data • Write a balanced chemical equation for each of the 3 reactions. #1: NaOH(s) + H2O(l) → NaOH(aq) + H2O(l) #2: HCl(aq) + NaOH(aq)→ NaCl(aq) + H2O(l) #3: HCl(aq) + NaOH(s)→ NaCl(aq) + H2O(l)

  7. Lab: “Calorimetry and Hess’s Law” 2. Analyzing Results • Add the first 2 equations from question #1 to get the equation for reaction #3: #1: NaOH(s) + H2O(l) → NaOH(aq) + H2O(l) + #2: HCl (aq) + NaOH(aq)→ NaCl(aq) + H2O(l) #3 NaOH(s) + HCl(aq)→ NaCl(aq) + H2O(l)

  8. Lab: “Calorimetry and Hess’s Law” 3. Explaining Events • Why does a plastic-foam cup make a better calorimeter than a paper cup? • A good calorimeter must insulate and not transfer (lose) heat. Plastic-foam cups are better insulators than paper cups and therefore make a better calorimeter.

  9. Lab: “Calorimetry and Hess’s Law” 4. Organizing Data • Calculate the change in temperature (ΔT) for each of the reactions. ΔT = Tfinal – Tinitial Example: ΔT1 =26.5°C – 21.5°C = 5.0°C ΔT2 = ΔT3 =

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