Problem: When a 4.25-g sample of solid ammonium nitrate dissolves in 60.0 g of water in a coffee-cup calorimeter, the temperature drops from 22.0 oC to 16.9 oC.You may want to reference (Pages 179 - 183) Section 5.5 while completing this problem.Calculate ΔH (in kJ/mol NH4NO3) for the solution process:NH4NO3(s) → NH4+(aq) + NO3-(aq)Assume that the specific heat of the solution is the same as that of pure water.Is this process endothermic or exothermic?

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We are asked to calculate ΔH (in kJ/mol NH4NO3) for the solution process:
NH4NO3(s) → NH4+(aq) + NO3-(aq)


Calculate heat released by water. 

q = mCTq = (60.0 g)(4.184 J/g-°C)( 16.9 °C-22.0 °C )q = (60.0 g)(4.184 J/g-°C)(-5.1 °C)

q = -1280.3 J


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Problem Details

When a 4.25-g sample of solid ammonium nitrate dissolves in 60.0 g of water in a coffee-cup calorimeter, the temperature drops from 22.0 oC to 16.9 oC.

A diagram shows two Styrofoam cups nested together.  The inside cup contains the reaction mixture in solution, and is covered by a cork stopper, through which a thermometer and glass stirrer are placed.

You may want to reference (Pages 179 - 183) Section 5.5 while completing this problem.

Calculate ΔH (in kJ/mol NH4NO3) for the solution process:
NH4NO3(s) → NH4+(aq) + NO3-(aq)

Assume that the specific heat of the solution is the same as that of pure water.

Is this process endothermic or exothermic?

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Endothermic & Exothermic Reactions concept. If you need more Endothermic & Exothermic Reactions practice, you can also practice Endothermic & Exothermic Reactions practice problems.

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