Calculate the change in enthalpy for the reaction- use 1.0g/ml as the density of

Question

Calculate the change in enthalpy for the reaction- use 1.0g/ml as the density of the solution and 4.18 J/(g degree C, as the specific heat capacity. 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 NO3 (8) NH (aq) NO3 (aq) In order to measure the enthalpy change for this reaction, 1.25 g of NHANO3 is dissolved in enough water to make 25.0 mL of solution. The initial temperature is 25.8 oCand the final temperature (after the solid dissolves) is 21.9 oC. you may want to reference (u pages 271-272) Section 6.7 while completing this problem.

Explanation / Answer

heat lost by water = m * s * (t2 - t1)

q = 25.0 * 4.18 * (21.9 - 25.8)

q = - 407.55 J

This amount of heat is absorbed by 1.25 g. of NH4NO3.

Moles of NH4NO3 = mass / molar mass = 1.25 / 80 = 0.0156 mol
Therefore enthalpy change of the reaction = q / n = 407.55 / 0.0156 = 26125 J/mol = 26. kJ/mol

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.