# Experiment 12: Calorimetry

1884 words 8 pages
| |
|Experiment 12- Calorimetry and Hess’s Law |
| |
| |
|Jenna Hyde |
|Lab partners:
J or .44kJ

qRXN=qHCL+qcal=2.8kJ+.44kJ=3.24kJ=3.2kJ

ΔHrxn=qrxn/nMg=3.2kJ/.00761mol=-420.499kJ/mol= -420kJ/mol

Mg(s)+2HCl(aq)(MgCl2(aq)+H2(g) ΔHrxn=-420kJ

Part C Calculations

Tf from graph by extrapolation: 26.0C

Mass of HCl:

[pic]

= 1.00 (g/mL)X 100.0mL= 100 g

ΔTCW=Tf-Ti= 26.0C-23.5C=2.5C

qHCl=mcΔTHCl=(100.0g)(4.184 J/gC)(2.5C)= 1046 J or 1.046 kJ=1000J or 1.0kJ

qCal=CcupΔTHCl=(65.6 J/C)(2.5C)= 164J or .164kJ=160J or .16kJ

qRXN=qHCL+qcal=1.0kJ+.16kJ=1.16kJ=1.2kJ

ΔHrxn=qrxn/nMgO=1.2kJ/.0127mol=-94.488kJ/mol=--94kJ/mol

MgO(s)+2HCl(aq)(MgCl2(aq)+H2O(l) ΔHrxn=-94kJ

Mg(s)+2HCl(aq)(MgCl2(aq)+H2(g) ΔHrxn=-420kJ

MgCl2(aq)+H2O(l) ( MgO(s)+2HCl(aq) ΔHrxn=94kJ

(1/2)(2H2(g)+O2(g)(2 H2O(l) ΔHf=-285.840kJ)

Mg(s)+(1/2)O2 (g)(MgO(g) ΔHf=-468.92kJ

[pic]

|Time (seconds) |Temperature (degrees|
| |Celsius) |
|0 |33 |
|30 |35.5 |
|60 |35.5 |
|90 |35 |
|120 |35 |
|150 |35.2 |
|180 |35.1 |
|210 |35.1 |
|240 |35 |
|270 |35 |
|300 |34.9 |
|330 |34.8 |
|360 |34.7 |
|390 |34.5

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