The Dissolving of Solid Sodium Hydroxide in Water
1. Measure out approximately 200 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. 3. 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
Constant initial temperature
| 24.5 degrees C
| 27.8 degrees C
Initial HCL temperature
| 25.2 degrees C
Mixed solution temperature
| 28.2 degrees C
In the lab, it was hard to get the measurements of the liquids exact, so they all were 5ml over what was asked for.
Show your work and write a short explanation with each calculation. 1. Write out a balanced "equation" for the process you investigated in Part I, including phase symbols.
NaOH(s) --> Na+(aq) + OH-(aq)
2. Calculate the number of moles of sodium hydroxide dissolved. Show your work. Moles of NaOH = 2.535 grams
NaOH X (1 mol/40.00 grams) =
0.06338 moles NaOH
3. Calculate the amount of energy involved in this dissolving process. Show your work.
205 g H2O
c = 4.184 J/gC
T2 = 27.8 C
T1 = 24.5 C
Heat gained by H2O = 205 g X 4.18 J/gC X (27.8 - 24.5)
= 2827.77 J
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