Purpose of Lab: To find the coefficients of two chemical reactants that appears in a balanced chemical equation using the continuous variations method.
Pre Lab Questions:
1. 2AgNO3(aq) + K2CrO4(aq) → 2KNO3(aq) + Ag2CrO4(s)
2. There is enough to make a valid conclusion because, on the graph, one can clearly see that the two lines intersect. Thus, one can also determine the mole ratio. The mole ratio is approximately 2:1 (AgNO₃ to K₂Cr₄).
1. Obtain 175mL of the bleach solution in a clean 400mL beaker and 175mL of Solution B in another beaker. 2. Measure the temperature of both solutions and record. The solutions should be the same temperature. If they are not, you will need to make a correction for the temperature difference. 3. Using a clean 10mL graduated cylinder, measure 5.0m: of NaClO and pour the solution into a Styrofoam cup. Using a clean 50mL graduated cylinder, measure 45.0mL of Solution B and add this to the Styrofoam cup. 4. Stir with a thermometer, and record the maximum temperature reached of the final solution in your data table. 5. Pour the solution out, rinse the cup and thermometer, and repeat steps 1-4 using a different ratio of the two substances, always keeping the volume at 50.0mL. 6. Continue testing various ratios until you have at least three measurements on each side of the one that gave the greatest temperature difference. 7. Plot your data on a graph, ∆T ℃ vs. Reactant volume (mL). 8. Draw two best fit straight lines, and determine where they intersect. Be sure to include the points at the 0:50mL and 50:0mL rations. If at any points do not fall close to the lines, repeat these measurements. Find the stoichiometric mole ration of reactants from the line of intersection on the graph.
Initial Temp of both: 23.5℃
Na2SO3 (mL)| NaClO(mL)| Max. Temp. (℃)|
45.0mL| 5.0mL| 28.9℃|
5.0mL| 45.0mL| 27.5℃|...