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Transcript of Deicer Lab
Data Day 1
Data Day 2
Determine the heat of solution for varying masses of MgCl2
1. Make a calorimeter with foam cups and temperature probe.
2. To find the qcal, mix known quantities of hot and cold water in the calorimeter to find ΔT by taking initial and final temperatures.
3. Solve for qrxn by mixing specified amount of solute with 15 g of water. Record initial temperature before mixing in solute and stir mixture until it reaches a final temperature.
4. Calculate ΔH of solution by dividing the qrxn by moles of solute for each specified mass value.
Masses tested include 0.5 g, 0.75 g, 1.0 g, and 1.5 g
Solution of water and MgCl2 is a highly exothermic process.
Higher the mass of MgCl2, higher the heat of dissolution
Molar Mass: 95.211 g/mol
Our Deicing Compound
Ability to lower the freezing point of water
Find the freezing point depression for varying masses of MgCl2
1. Measure out varying masses of MgCl2
2. Put each sample into a test tube. .
3. Put 15 mL of deionized water into each test tube and stir.
4. Prepare four beakers of 100.0 mL of water. Add ice to get water below 0ºC
5. Place one test tube into each beaker.
6.Collect temperature readings until water reaches freezing point depression equilibrium.
7. Repeat step 6 for each test tube and beaker.
Overall, the greater the mass of MgCl2, the greater the freezing point depression.
Tested masses include 0.5 g, 0.75 g, 1.0 g, 1.5 g, and 2.0 g
Unable to freeze the 2.0 g solution
Measured values did not deviate much from calculated values (i.e. the calculated freezing point for the 0.5 g solution was 1.98 degrees Celsius and the experimental value was 2.3 degrees Celsius)
Cost per unit
Enthalpy of dissolution
Data Day 3
Find freezing point depression and heat of dissolution for alternative masses of MgCl2.
Repeat procedures from days 1 and 2.
Masses tested include 0.25 g, 1.25 g, and 1.75 g
Results were in line with results from days 1 and 2
The greater the mass of MgCl2, the greater the freezing point depression
High heat of dissolution makes it an excellent deicer
Low cost per unit: $0.000012 per gram
Harmful if ingested- may be a problem to animals and plants if absorbed or consumed from runoff
Sources of Error
Magnesium chloride is very anhydrous, so when we measured out the masses we were adding to the 15mL of water, some of the particles stuck to the paper, thus losing some of the mass of the solute which would in turn make the value of Delta T smaller.
We did not use the same scale between all three days of experiments which could cause some variation in the masses of the solute being added to the solvent seeing as not every scale is calibrated quite the same
When adding the MgCl2 to the water in the Day 2 experiment, it was inevitable that some of the heat created when the compound was added to the water would be lost due to the time it took to put the styrofoam cup on the top of the calorimeter. The loss of this heat would decrease the value of Delta H.