Heat of Reaction Lab
Taken from WolframAlpha
Uncertainty Propagation
Moles of Fe
0.07501 moles (± 1.79067E-05 moles)
Molar Heat Change
-31.36 kJ ± 0.15 kJ
When the probe was placed into the Styrofoam, it took a large leap during the first four seconds by immediately jumping from 25 °C to 26.5 °C. It climbed at a slower rate to 27.5°C in the next 8 seconds then “decelerated” from 27.5 to 27.9 in around the next 18 seconds. When the iron was added at 30 seconds, the temperature flirted with fluctuations around the 28 °C area, then after a few ...
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Uncertainty Propagation
Moles of Fe
0.07501 moles (± 1.79067E-05 moles)
Molar Heat Change
-31.36 kJ ± 0.15 kJ
When the probe was placed into the Styrofoam, it took a large leap during the first four seconds by immediately jumping from 25 °C to 26.5 °C. It climbed at a slower rate to 27.5°C in the next 8 seconds then “decelerated” from 27.5 to 27.9 in around the next 18 seconds. When the iron was added at 30 seconds, the temperature flirted with fluctuations around the 28 °C area, then after a few seconds took a sudden jump to over 29 °C. It instantaneously dropped back down to around 28.5 °C, but then begun another steady increase as the reaction between hydrochloric acid and iron II took place. As an exothermic reaction, the increase in temperature was caused by the heat, which was passed from the reaction into the hydrochloric acid.
However, because heat was lost from the system, ΔH is negative. True enough, our calculated values of -31.36 kJ ± 0.15 kJ backed up this claim. Heat was lost from the system as soon as the temperature rose above the temperature of the surroundings; in this case it was 28 °C. The maximum temperature recorded was around 29.14 °C, which was lower than the true value obtained in a perfectly insulated system. Our projected maximum temperature allowing for heat loss (29.4°C), was only around 0.26 °C more than our obtained maximum temperature. Extrapolating the line was an attempt to make up for some of the heat loss, but it is simply impossible because calculated values assume that there is no heat loss from the system, all heat is transferred to the water and the solution contained exactly 150 mL of hydrochloric acid. Obviously, this wasn’t the case as it is impossible for each one of these three to occur under our lab conditions. The heat released or absorbed by the reaction can be measured from the temperature change of the hydrochloric acid, but there are still possibilities of heat escaping. In fact, our calculated heat of reaction, -31.36 kJ ± 0.15 kJ , was so far away from the accepted value of -157.2 kJ (according to ). There were several limitations and weaknesses that added this huge inaccuracy to our heat of reaction.
Unfortunately, our heat of reaction was so far off from the accepted rate of reaction. Hopefully, if these aforementioned improvements are made next time around, the calculations will be a lot more accurate.
Seems relatively fast for a time uncertainty, but it was measured by the computer so we use the smallest scale division.
Temperature recording was very accurate to 10 decimal places. IT has more decimals than the time, but it’s okay as long as it’s the same decimal places per column. Would have been incorrect to limit the decimal places of temperature to 2 d.p. or add decimal places of time to 10 d.p. Rounding can occur during the processed data as shown in Δ Temperature of HCl.
