Thermo Chemistry Lab

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Thermochemistry Lab
We predict that two different physical changes (dissolving of a chemical substance in water) will produce energy changes; one exothermic and one endothermic. We predict that the temperature change will be affected by the change in system (open vs. closed) will be as follows: the temperature change in the closed system will be greater than that of the open system. Materials

Refer to attached sheet
Refer to attached sheet

Substance Added| Temp Before| Temp After| Change in Temp(Celsius)| Observations| Open - Calcium Chloride| 24| 30| 6| translucent , slightly murky| Open - Ammonium Nitrate| 24| 30| 6| translucent, slightly murky| Closed - Calcium Chloride| 24| 18| 6| transparent|

Closed - Ammonium Nitrate| 24| 17| 7| transparent|

i) Calcium Chloride: Q = (100) (4.184) (6) = 2510.4
Ammonium Nitrate: Q = (100) (4.184) (7) = 2928.8

ii) NH4NO3: (14.0067) + 4(1.00794) + (14.0067) + 3(15.9994) = 80.04336 g/m 10 g80.04336 g/m = 62,00500,271
CaCl2: (40.078) + 2(35.453) = 110.984 g/m
10 g110.984 g/m = 1,25013,873m

a. NH4NO3 (aq) NH4(aq) + NO3(aq)

b. CaCl2(aq) Ca(aq) + Cl2(aq)

1. Some sources of error in this lab include the following. After stirring the water there were still particles of the substance left at the bottom, which means the reaction didn’t fully occur. The thermometers we used weren’t accurate because the temperature in the room changed as well as the scale was not easy to see and inaccurate. The amount of substance we used in the reactions could have been off because the scales only went to 2 decimal places. 2. Some improvements in this lab could be fully stirring the substance into the water, use a more accurate thermometer (such as a laser thermometer), use an actual calorimeter, and use a more accurate scale.

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