The change in enthalpy for the combustion of magnesium metal
Abstract
========
Hess’s law of heat summation states that the value of DH for a reaction is the same whether it occurs directly or as a series of …show more content…
After a few moments, the final temperature was recorded and DT determined. This process was then repeated. On the second trial, the Mg ribbon did not completely dissolve and the results were thrown out. The third trial
(referred to as the second in the following analysis due to the exclusion of the previous one) was successful, and measurements can be seen below.
We then moved onto the second reaction using magnesium oxide and hydrochloric acid in the fume hood. We measured 200.1 mL of HCl and placed it in the calorimeter, and initial temperature reading was taken. Next, we measured 1.07 g of magnesium oxide, using a balance in the fume hood, added it to the HCl in the calorimeter, and shut the lid quickly to conserve heat. This mixture was “swirled” and allowed a few moments to react. The final temperature was recorded and DT determined.
GRAPH GRAPH
Throughout this investigation data was collected and placed on the above tables to be used in the calculations below.
Calculations:
Given:
H2 + 1/2O2 ® H2O DH = -285.8 kJ/mol
Mg + 2HCl ® MgCl2 + H2
Trial 1:(not used)
.01g. Mgx 1mol Mg = .0004 mol
Mg 198.5 L =
198.5g.
24.305 g. …show more content…
Using the following givens we were capable of calculating our percent error at different stages in the investigation as well as our final answer:
Mg + 1/2O2 DH = -601.8 kJ/mol Mg
We found our change in enthalpy for magnesium oxide had a 13.2% error, while our change in enthalpy for magnesium had only a .682% error.
Our final answer was fairly accurate, only having a 2.46% error.
These errors may be accounted for by inaccurate measurements, mathematical mistakes, incomplete reactions, poor heat collection, incorrect recording of data, and poorly calibrated tools. To avoid such error one should label all materials, check each tool before use, take extra care in reading and recording of measurements, double check all calculations, and most of all be patient, labs take time and a rushed procedure leads to inaccurate data and incorrect analysis.
Sources Cited
Cartwright, H.(last revised 2002, November 5). Chemical and other
Safety Information. The Physical and Theoretical Chemistry Laboratory,
Oxford University.
[online]. (accessed 2002,
December,
Abstract
========
Hess’s law of heat summation states that the value of DH for a reaction is the same whether it occurs directly or as a series of …show more content…
After a few moments, the final temperature was recorded and DT determined. This process was then repeated. On the second trial, the Mg ribbon did not completely dissolve and the results were thrown out. The third trial
(referred to as the second in the following analysis due to the exclusion of the previous one) was successful, and measurements can be seen below.
We then moved onto the second reaction using magnesium oxide and hydrochloric acid in the fume hood. We measured 200.1 mL of HCl and placed it in the calorimeter, and initial temperature reading was taken. Next, we measured 1.07 g of magnesium oxide, using a balance in the fume hood, added it to the HCl in the calorimeter, and shut the lid quickly to conserve heat. This mixture was “swirled” and allowed a few moments to react. The final temperature was recorded and DT determined.
GRAPH GRAPH
Throughout this investigation data was collected and placed on the above tables to be used in the calculations below.
Calculations:
Given:
H2 + 1/2O2 ® H2O DH = -285.8 kJ/mol
Mg + 2HCl ® MgCl2 + H2
Trial 1:(not used)
.01g. Mgx 1mol Mg = .0004 mol
Mg 198.5 L =
198.5g.
24.305 g. …show more content…
Using the following givens we were capable of calculating our percent error at different stages in the investigation as well as our final answer:
Mg + 1/2O2 DH = -601.8 kJ/mol Mg
We found our change in enthalpy for magnesium oxide had a 13.2% error, while our change in enthalpy for magnesium had only a .682% error.
Our final answer was fairly accurate, only having a 2.46% error.
These errors may be accounted for by inaccurate measurements, mathematical mistakes, incomplete reactions, poor heat collection, incorrect recording of data, and poorly calibrated tools. To avoid such error one should label all materials, check each tool before use, take extra care in reading and recording of measurements, double check all calculations, and most of all be patient, labs take time and a rushed procedure leads to inaccurate data and incorrect analysis.
Sources Cited
Cartwright, H.(last revised 2002, November 5). Chemical and other
Safety Information. The Physical and Theoretical Chemistry Laboratory,
Oxford University.
[online]. (accessed 2002,
December,