Heat of reaction lab Assignment

Heat of reaction lab Assignment Words: 1764

Calculating the Energy of an Acid-Base Reaction Written by: Alex Screaming Group members: Grace Gilberts, Shannon Animosity Abstract: The purpose of this experiment was to properly calculate the heat of an acid-base reaction. To calculate the energy of this reaction a coffee-cup calorimeter was made. Two different calorimeters were made and each Individually tested. Once the heat capacity of each calorimeter was measured then a reaction of An(OH) and H2O(ASS) occurred in the calorimeters. The change in energy was then calculated using the calorimeter.

It was calculated in the first calorimeter to have a heat change of -ASK]/ Mole and in the second calorimeter the heat change was -71 K/mole. The percent error was 13. 7 percent for calorimeter one and 23. 8 percent for calorimeter two. Introduction: The objectives of the heat off reaction lab were to be able to design and construct a calorimeter and calculate the heat of an acid base reaction. The first day (don’t say this) consisted of constructing a calorimeter, which had a low heat capacity. The lower the heat capacity of a calorimeter the more accurate the results of the reaction would be.

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The design of the calorimeter had to be made with a few specific materials. The materials ranged from Styrofoam cups to duct tape. Styrofoam was used because it is lightweight and insulates extremely well. Building blocks called monomers. When Styrofoam is being made gas in blown into the Polystyrene thus creating thousands of captured gas bubbles. This allows little heat transfer because the gas molecules have a farther distance away to travel and transfer energy. Also the solid polystyrene contains large molecules that take large amounts of energy to move thus energy transfer is more difficult.

These illustrate some reasons why the Styrofoam was used as a calorimeter. Calculating the heat of a reaction and the change in energy is very important because when designing new materials such as Styrofoam, heat is either absorbed or expelled. When trying to make materials in mass quantities that energy released must be accounted for. This is being used daily in Jobs like chemical engineers who must make processes for chemicals and materials to be made. If the heat and energy is not accounted for then it could potentially be dangerous if too much is eyeing made and therefore too much energy being released.

This cannot only cause damage to input materials but also very harmful to people. The theoretical amount of energy released per mole was around -JOKE/mole. This was calculated using the formula change in enthalpy of products minus the change in enthalpy of the reactants. This means that for every mole of product formed there should be 57 kilojoules of energy released. However, with error this number will not be reached but should be fairly close. Experiment: Materials Needed- The materials needed for this experiment on the first day included: Styrofoam, duct tape, scissors, single ply cardboard, tin foil, temperature probe and a laptop.

These were the physical materials needed to construct the calorimeter. However, water and a hot plate was needed to calculate the heat capacity of the calorimeter. On the second day (NOPE), the two calorimeters were needed along with the acid and base to be reacted. The acid consisted of MM HASPS and the base consisted of MM An(OH). After only a calculator was needed for calculating the final enthalpy of the reaction. Constructing of Each Calorimeter- When the lab was presented a well made design is needed. The design was chosen to have a calorimeter with a Styrofoam cup as the base and then a cardboard lid.

After the lid was made to fit atop the cardboard duct tape would be used to secure the lid down. However, it could not be taped all of the way around because it still needed to be opened to allow the chemicals to be poured into the calorimeter. Also tin foil was quickly wrapped around the cup. Then a hole was constructed in the middle of the lid to allow the temperature probe to be inserted into the calorimeter. This design would create a closed system. Styrofoam would insulate the reaction well. Keeping the reaction closed would allow less heat to escape through the top of the calorimeter.

The design was slightly altered for the second calorimeter. Tin foil was used and wrapped around the coffee cup. The tin foil correctly wrapped would Just add another layer of insulation. The second calorimeter had a better quality than the first, however, the designs were very similar. Testing to discover the specific heat- After each of the calorimeters was created, each had to be tested to calculate the specific heat of the calorimeter. Water was needed at different temperatures. The ass of the cold water would be around 25 ml and the mass of the hot water would there could be.

Three trials were run for each calorimeter. The water was heated and measured until it was close to 70 degrees Celsius. Then the heated water was poured into the calorimeter, which already contained the cold water at around room temperature. The temperature was then graphed until the temperature of the water leveled out and final temperature was recorded. From those temperatures the heat capacity of both calorimeters was calculated. Heat of Acid-Base Reaction- On the second day of the lab, the Acid-Base reaction occurred in the calorimeters. M HASPS was used and MM An(OH) was as well. A balanced chemical reaction of these is illustrated by the equation of: . Thus ml of An(OH) was used along with 5 ml of HASPS. The acid was put into the calorimeter first and initial temperature readings were made. This would be the initial temperature of the acid and of the calorimeter. The base was then measured out initial temperature was measured. Once each data point was recorded the base was then poured into the calorimeter and the lid was closed. Once the reaction began the temperature was graphed per unit of time.

The graph leveled out and the final temperature was recorded. Each of the calorimeters had three trials. After each of the trials the calorimeter was washed out thoroughly. If any acid or base were still in the calorimeter then it could produce an outlier and disrupt any future calculations because then there would be excess amounts of either acid or base. Once the final temperature was recorded the energy of the reaction was calculated and the change of enthalpy was then calculated for each of the trials and calorimeters and averaged.

More effort and better design led to a calorimeter, which would lead to ore accurate data. The reason a low heat capacity is important because then less energy is given to the calorimeter per degree of temperature change. Using the equations the assumption was made that heat capacity of can be illustrated as, and because it is known it can be calculated the heat capacity of each calorimeter which is shown above. The specific heat capacity of water is a constant of 4. 184]/ (grams*degrees). There were few limitations in this section of the experiment.

One limitation would be when pouring the hot water into the calorimeter. When taking he hot water off of the hot plate some heat was lost because it was open to the room temperature air. This caused some error in the data and precautions were made to try to reduce this effect however the limitation couldn’t be completely eliminated. Some changes, which could have been made, would be to put another cup of Styrofoam on to better insulate the reaction. Also a higher quality of lid could have been made. Change in Enthalpy- The change in enthalpy can be described as the energy released in a reaction.

The reason this reaction releases energy is because the energy in the bonds being broken is greater than the energy needed to form new bonds. Table three and table four show this to be true. A negative change in enthalpy indicates a release in energy. The energy is caused by the bonds being broken in each of the molecules to form the new molecules. If the sign of enthalpy were positive then the reaction would have needed to absorb energy to form the bonds. In this reaction of two molecules of liquid water are formed. ml of Noah were used along with ml of HASPS.

This would mean either of the chemical are not a change in temperature could be calculated. This is important because and . The solution could be considered to have the same specific heat capacity of water because it is an aqueous solution and it is close to the specific heat of water for it to be negligible. Once the grin was calculated the moles of product formed, which was . 06 moles, was used to divide the energy by the moles to discover the change of enthalpy. The change in enthalpy is shown in tables 3 and 4 to be -64. AKA/mol and -70. AKA/mol for calorimeter 1 and 2 respectfully. The theoretical enthalpy for this reaction is -JOKE/mol.

This would mean the percent error is 13. % for the first calorimeter and 23. 8% for the second one. The theoretical enthalpy was calculated using the formula. Therefore for every one mole of water formed JOKE of energy is released. Some error was introduced into the lab. On one trial for calorimeter two the calorimeter tipped causing more reaction to occur because of the stirring of chemicals. However, this should not have caused much error because it occurred after the graph had already leveled. A limitation of this section could be human error and false interpretation of graphs and data.

One extension is to see whether a hanger in amounts of acid or base used affects the enthalpy of the reaction. This would leave one excess and the other a limiting reactant. Conclusion: Based on the materials needed the best design was hypothesized to be a Styrofoam cup wrapped in tin foil with a cardboard lid closing the top of the cup and secured by duct-tape. This would create a closed system, which would allow less heat to leave the calorimeter and creating more accurate data. After three trials using differences of hot and cold water the heat capacity of calorimeter 1 and 2 were 13. J/degree and 10. J/degree respectfully.

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