Exercise 6.76 6 of 11 Constants 1 Periodic Table Part A Instant cold packs, ofte

Question

Exercise 6.76 6 of 11 Constants 1 Periodic Table Part A Instant cold packs, often used to ice athletic injuries on the field, contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves according to the following endothermic reaction NH,NOs(a) NH; (aq) + NO, (aq) Calculate the change in enthalpy for the reaction in kilojoules per mole. (Use 1.0 g/mL as the density of the solution and 4.18 J/g. C as the specific heat capacity.) Express your answer to two significant figures and include the appropriate units Ma In order to measure the enthalpy change for this reaction, 1.25 g of NH4NOs is dissolved in enough water to make 25.0 mL of solution. The initial temperature is 25.8 and the final emperature (after the solid dissolves) is 21.9 C AHValue Units Submit Request Answer Provide Feedback Next >

Explanation / Answer

No of mol ofNH4NO3 dissolved = w/M = 1.25/80 = 0.0156 mol

mass of solution = d*v

                 = 1*25.0

                 = 25 g

heat released(q) = m*s*DT

                 = 25*4.18*(25.8-21.9)

                 = 407.55 joule

                 = 26.1 kj/mol

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