Experiment 1: Determine the Enthalpy Change of a Chemical Reaction Lab Results F

Question

Experiment 1: Determine the Enthalpy Change of a Chemical Reaction

Lab Results

Fill the table below with your results from the first trial.

Data Analysis

Calculate the mass of the contents of the calorimeter in trial 1.

50.138 grams

Calculate the number of moles of magnesium used in trial 1. The molar mass of magnesium is 24.305 g/mol.

0.041 moles

Calculate the change in temperature in trial 1.

13 °C

Calculate the heat of reaction in trial 1.

Calculate the enthalpy of reaction using your results from trial 1.

Calculate the heat of reaction in trial 3.

Calculate the enthalpy of reaction using your results from trial 3.

Conclusions

Is the reaction of magnesium and hydrochloric acid exothermic or endothermic?

Endothermic

Suppose a student performed the trial 1 experiment in his classroom laboratory. After adding the magnesium, he forgot to close the lid. How do you expect his final temperature after the reaction will compare to the one you measured in this lab?

The temperature would be less compared to the one measured in the lab because the outside air would effect the temperatue bringing it down.

Experiment 1:

Mass of empty Calorimeter: 18.600 g

Temp. of Calorimeter: 21.5 C

Mass of caliometer with 50 mL M Hydrochloric Acid: 68.600 g

Temp: 21.5 C

Mass of caliometer with 0.150 g Magnesium: 68.738 g

Temp: 34.5 C

Experiment 2:

Mass of empty Calorimeter: 18.600 g

Temp. of Calorimeter: 21.5 C

Mass of caliometer with 50 mL M Hydrochloric Acid: 68.600 g

Temp: 21.5 C

Mass of caliometer with 0.250 g Magnesium: 68.829 g

Temp: 43.2 C

Experiment 3:

Mass of empty Calorimeter: 18.600 g

Temp. of Calorimeter: 21.5 C

Mass of caliometer with 50 mL M Hydrochloric Acid: 68.600 g

Temp: 21.5 C

Mass of caliometer with 0.250 g Magnesium: 68.921 g

Temp: 51.8 C

mass of empty calorimeter (g) 18.600 initial temperature in the calorimeter (ºC) 21.5 final temperature in the calorimeter (ºC) 34.5 mass of the calorimeter and its contents after the reaction(g) 68.738

Explanation / Answer

From the trial 1 data

heat of reaction = mCpdT

                          = 50.138 x 4.184 x 13

                          = 2.73 kJ

enthalpy of reaction = heat/moles

                                = 2.73/0.041

                                = 66.515 kJ/mol

Reaction is exothermic in nature : heat is released, Temperature at the end is hiher than intial temperature due to heat released.

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