Question

i am needing help with question 4 and 5. anything else helps

Name Experiment 7 Calorimetry Postlab: Questions 25 points possible Section (day&time) Instructor Due date Answer the following questions using complete sentences and support your answers with swers calculations, if desired. Attach additional pages as necessary. Handwritten or typed an are acceptable.(5 pts per question) 1. If som e of your hot metal remained in the test tube when it was transferred to the eter, would its calculated molar mass be greater than, less than, or unchanged from your answer. Note: Only consider the change is mass of metal, not calorim the actual value? Explain the change in heat transfer. If you spilled some of your measured quantity of water before adding it to the calorimeter would the calculated value of AH, for your salt be greater than, less than, or equal to the actual value? Explain your answer 3. Given that the enthalpy of formation of water is -285.83 kJ/mol,the enthalpy of formation of copper sulfate is -771.36 kJ/mol, and the enthalpy of formation of copper sulfate pentahydrate (CuSO4-5H2O) is -2279.6 kJ/mol, determine whether hydrating anhydrous copper sulfate to form copper sulfate pentahydrate is an endothermic or exothermic process 4. A 1.00 g sample of MgCl2 produced a 10.00 °C increase in a calorimeter charged with 40.0 mL of deionized water. The specific heat of MgClh is 0.750 JP C g. What is the value of A,H for MgClh? Use your result from #4 and data Table 7.1 to calculate the value of 4He for Mg2+(as). Note: You must write out the formation equations of all products and reactants and sum to find the change in enthalpy for the formation of the cation (like example 7.3). Failure to do so will result in zero credit 5. REQUIRED: Write a conclusion section for the Calorimetry lab on a separate sheet of paper. (Reference Appendix on guidelines for laboratory writing) (20 pts) 6. 125 s Time (s) data shown from the screen capture of the Logger Pro software has f 21.3 °C and a calculated maximum of 22.1 °C for a total change in tem cted thermodynamic values for salts used in this experiment. A¡H (kJ/mol) -314.43 356.56 -436.75 -411.15 -327.90 -287.78 -641.32 -167.16 55.2 Species NH4CI (s) NH4NO3 (s) KCI (s) NaCl (s) KI (s) Nal (s) MgCl2(s) Cl (aq) I(aa) NO3 (aq) 1.57 1.74 0.688 0.864 0.319 0.348 0.750 11.3

Answer 1

4. q for MgCl2 = m c ∆T = 40 × 0.75 × 10 = 300 J

∆sH = q/ moles of MgCl2

Moles of MgCl2 = 1/ 95.211

∆sH = 300/ 1/95.211= 28563.3 J/mol

5. ∆fH of MgCl2 = -641.32 kJ/mol

∆dH of MgCl2 = -(-641.32) = 641.32 kJ/mol

∆H(aq) = ∆dH + ∆sH = 641320 + 28563.3 = 669.8833 kJ/mol