Reaction 1: Temperature change is really slow. Reaction 2: Temperature raises a lot, but not very fast.
Reaction 3: Temperature increases very fast. It jumped all the way to 26°C in 3 seconds right after pouring 50.0mL of 1.0M NaOH into 50.0mL of 1.0M HCl.
Table #4: Results collected by Zheting and Melissa:
Processing Data:
1. Calculating mass
Note: Mass = Density x Volume
Example calculation: Mass of reaction 1
=2.93 g of NaOH + (1g/ml x 100 ml) (H2O) = 2.93g + 100g = 102.93g = approx. 103g
Uncertainty:
Solid NaOH’s mass uncertainty = + 0.005g Density uncertainty = 0
Uncertainty of mass = + 0.005g + 0 = + 0.005g. Results collected by Rhona and Laura:
2. Calculating ■t
Note: ■t = t2 – t1
Example Calculation:
■t of Reaction 1 = 22°C - 21°C = 1°C
Uncertainty: + 0.2 °C 0.2 + 0.2 = 0.4.
■t has an uncertainty of 0.4 °C
Results collected by Rhona and Laura:
Results collected by Zheting and Melissa:
3. Calculating q
Note: q = Cp · m · ■t (Heat Capacity [Cp] = 4.18J/g°C)
Example calculation:
q of Reaction 1 = 4.18 J/g x 103g x 1°C = 430.54 J 1000 J = 1 kJ , so 430.54J = 430.54 / 1000 = 0.431 kJ
4. Calculating ■H
Note: ■H = -q
Sample calculation:
■H of Reaction 1 = - (0.431kJ) = -0.431 kJ
Results collected by Rhona and Laura:
5. Moles of NaOH
Note: NaOH’s molar mass is 23+16+1 = 50 g/mol
Results collected by Rhona and Laura:
Reaction 1: 2.93g NaOH
Mol = mass/molar mass
Mol = 2.93g/50g/ml = 0.0586 mol
Reaction 2: 2.87g NaOH
2.87g/ 50g/m = 0.0574 mol
Reaction 3: 50ml of NaOH
50g / 50 g/m = 1 mol
Results collected by Zheting and Melissa:
Reaction 1: 1.97g NaOH
Mol = mass/molar mass
Mol = 1.97g/50g/ml = 0.0394 mol
Reaction 2: 2.87g NaOH
1.98g/ 50g/m = 0.0396 mol
Reaction 3: 50g NaOH
50g / 50 g/m = 1 mol
6. ■H / mols of NaOH
Note: ■H is taken from part 4 and mols of NaOH is taken from part 5.
7. Theoretically, heat of reaction 1 + heat of reaction 3 = heat of reaction 2.
Results collected by Rhona and Laura:
Heat of Reaction 2: -94.7kJ/mol
Combined heat of reaction 1 and 3: -93.3kJ/mol
