The Dissolving of Solid Sodium Hydroxide in Water Procedure

9 September 2016

Measure out approximately 205 mL of distilled water and pour it into the calorimeter. Stir carefully with a thermometer until a constant temperature is reached. Record the volume of water and the constant initial temperature of the water on your data table. 2. Place a plastic measuring trough on top of the digital balance, and then zero the balance (press the tare button) so that the mass of the trough will be “ignored” and will not be added to the total mass measured by the balance.

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Measure out approximately three to five scoops of solid sodium hydroxide and record the mass to your data table. 4. Place the solid sodium hydroxide into the water in the calorimeter and replace the lid immediately. Stir gently until the solid is completely dissolved and record the highest temperature reached. Data and Observations Distilled Water Volume 205. 2 mL Constant Initial Temperature 24. 2°C NaOH Mass 2. 535g Final Temperature 27. 8°C Calculations 1. Write out a balanced “equation” for the process you investigated in Part I, including phase symbols. NaOH(s) + H2O(l) -> Na+(aq) + OH-(aq) 2.

Calculate the number of moles of sodium hydroxide dissolved. Show your work. 3. Calculate the amount of energy involved in this dissolving process. Show your work. qsurroundings = -qsystem qsystem = -3. 126kJ 4. Determine the enthalpy change, per mole of sodium hydroxide dissolved. Show your work. Part II: The Reaction of Sodium Hydroxide Solution with Hydrochloric Acid Procedure 1. Measure out approximately 100 mL of 0. 50 M hydrochloric acid solution and 100 mL of 0. 50 M sodium hydroxide solution. Record both volumes on your data table. 2. Pour the hydrochloric acid solution into the calorimeter.

Measure and record the initial temperature of each solution and record on your data table. 3. Add the sodium hydroxide solution to the acid solution in the calorimeter and immediately replace the lid of the calorimeter. Stir the mixture and record the highest temperature reached. Data and Observations HCl Solution 100. 9mL NaOH Solution 100. 9mL Initial HCl Temperature 25. 2°C Mixed Solution Temperature 28. 2°C Calculations 1. Write out a balanced equation for the reaction you investigated in Part II, including phase symbols. NaOH(aq) + HCl(aq) ->  NaCl(aq) + H2O(l) 2. Determine the enthalpy change of this reaction.

Show your work. 4. Using the accepted values of the processes you’ve examined, would your estimation of the enthalpy change for the reaction of solid sodium hydroxide in aqueous hydrochloric acid change from the prediction you made in question one? Yes, because somehow my data is way off with a 98. 2% error. The enthalpy change should be almost twice my initial prediction. 5. Give a detailed explanation, using what you know about bonds and forces of attraction, for the enthalpy changes you observed in parts I and II of this lab.

NaOH is an ionic bond and is stronger than a covalent bond, so naturally it would require a higher amount of energy to break apart. 6. If the hole for the thermometer in a calorimeter is wider than the diameter of the thermometer, leaving a gap between the lid and the thermometer itself, how do you think this would this affect the temperature change observed in the experiment? How would this affect the calculated enthalpy change? Heat would escape through the gap and you would observe lower temperatures than what would actually occur and result in lower enthalpy change.

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