2b. Enthalpy of Salts Lab Assignment PDF

Preview

Summary

Lab assignment with collected data and tables....

Description

Keep all data below. Once you have at least two good trials for a given salt, enter your selected trials (at least 2 per salt) on the group online. Be sure to select the correct section and lab location. Table 1. Determination of heat and enthalpy of solvation. T

M

Volu

Ti

Tf

Type of

ri

Salt

as

me of

(°C)

(°C)

Reaction

qrxn (J)

(kJ/m

ΔH

al

s of

Wate r

(endo/ex o)

ol)

Sa

(mL)

lt (g) 1

MgSO 4

1. 00 1

24.9

21. 73

26.3 8

exo

-0.496 27

-59.68

2

MgSO

1.

24.5

22.

26.9

exo

-0.519

-62.48

4

00

07

5

21.

18.3

24

0

21.

18.8

79

6

10

0 1

NH4N

1.

O3

00

25.1

endo

0.3181

25.26

1

8 2

NH4N

1.

O3

00

25.0

endo

0.3182 5

6

MgSO4 Trial 1 (Molar mass: 120.37 g/mol) Calorimeter: 1.380 g Rxn T: 100 s Mass of MgSO4: 1.001 grams (8.316 x 10^-3 moles) 24.9 mL of water Ti (°C): 21.73 Tf (°C): 26.38 Total Mass of solution & Calorimeter: 26.912 - 1.380 = 25.532 grams qrxn (J): - (25.532 g)(4.18 J/g*°C)(26.38–21.73 °C) = -496.27 J = -0.49627 kJ

25.32

ΔH (kJ/mol): (-0.49627 kJ) * [(120.37 g/mol)/(1.001 g)] = -59.68 kJ/mol Trial 2 Rxn T: 110 s Mass of MgSO4: 1.000 grams (8.308 x 10^-3 moles) 24.5 mL of water Ti (°C): 22.07 Tf (°C): 26.95 Total Mass - Calorimeter = Final Mass: 26.681 grams - 1.380 = 25.301 grams qrxn (J): - (25.301 g)(4.18 J/g*°C)(26.95–22.07 °C) = -519.10 J = -0.51910 kJ ΔH (kJ/mol): (-0.51910 kJ) * [(120.37 g/mol)/(1.000 g)] = -62.48 kJ/mol

NH4NO3 Trial 1 (Molar mass: 80.05 g/mol) Calorimeter: 1.380 g Mass: 1.008 g (1.259 x 10^-2 moles) 25.1 mL water Ti (°C): 21.24 Tf (°C): 18.30 Total Mass - Calorimeter = Final Mass: 27.265 - 1.380 = 25.885 g qrxn (J): - (25.885 g)(4.18 J/g*°C)(18.30–21.24 °C) = 318.11 J = 0.31811 kJ ΔH (kJ/mol): (0.31811 kJ) * [(80.05 g/mol)/(1.008 g)] = 25.26 kJ/mol Trial 2 Mass: 1.006 g (1.257 x 10^-2 moles) 25.0 mL of water Ti (°C): 21.79 Tf (°C): 18.86

Total Mass - Calorimeter = Final Mass: 27.365 - 1.380 = 25.985 g qrxn (J): - (25.985 g)(4.18 J/g*°C)(18.86–21.79 °C) = 318.25 J = 0.31825 kJ ΔH (kJ/mol): (0.31825 kJ) * [(80.05 g/mol)/(1.006 g)] = 25.32 kJ/mol

KCl Trial 1 (Molar mass: 74.55 g/mol) Rxn T: 150 s Calorimeter: 1.380 g Mass: 1.002 g (1.344 x 10^-2 moles) 24.8 mL of water Ti (°C): 21.56 Tf (°C): 19.28 Total Mass - Calorimeter = Final Mass: 27.044 -1.380 = 25.664 g Trial 2 Mass: 1.000 g (1.341 x 10^-2 moles) 25.0 mL of water Ti (°C): 21.55 Tf (°C): 19.39 Total Mass - Calorimeter = Final Mass: 27.171 - 1.380 = 19.791 g Section Data

Collect the data from your section and calculate the values to complete the table below. You should use excel or google sheets to compile data and calculate averages, and then either copy your final answers below or link your file. It is expected that you will evaluate the data and remove outliers, questioning each result. Table 2. Enthalpy of salts. Salt

Formula Weight

Type of

qrxn

ΔH

(g/mol)

Reaction

(J)

(kJ/mol)

NH4Cl

53.49

endothermic

326.0

17.37

9 KCl

74.55

endothermic

239.7

17.85

BaCl2

208.23

endothermic

6.52

1.37

NaNO

84.995

endothermic

222.8 8

18.91

101.10

endothermic

294.9

29.73

exothermic

3 -337.

-37.31

3

KNO3 CaCl2

110.99

19 NH4N

80.05

endothermic

120.63

exothermic

O3 MgSO

287.9 2 -572.

22.96 -68.77

46

4

MgCl2

203.30

exothermic

-45.6 8

-9.21

Did you eliminate any data? Why or why not?

●

○

No; most of the data points were quite similar for my section. It was not necessary to remove any data points, as there were no outliers.

Observations and measurements for reusable hotpack: Qualitative: Before flipping disk: ●

The hot pack is reddish-orange,

●

squishy and jelly-like

●

noticeable bubbles

●

It is not hot to the touch (feels like room temp.)

●

There is a metal disk inside

After flipping disk: ●

The hot pack became a light orange

●

Became a chunky, hard texture

●

Feels very hot

Quantitative:

Tinitial (°C): 24.02

Tfinal (°C): 57.09 Temp. Change (°C): 33.07...