# AP Chemistry – Class 46

Lab: Ratio of Reactants in Solution

- Period E – Wednesday, December 4
- Period F – Thursday, December 6

The lab is an example of the stoichiometry of a reaction in solution. Two solutions will be mixed in varying ratios with and the temperature change recorded for each trial. From this data it is possible to determine the mole ratio of the participants in the reaction.

Notes to consider for the procedure:

- It is critical to record the temperature of the solutions before mixing. These starting points will serve as the baseline for temperature rises needed to determine the change.
- The starting temperature for each trial is a weighted average of the starting temperatures of each of the two solutions used.
- You will need to know the theory behind each reaction as well as how to perform each of the calculations.
- Be mindful of the reaction solutions as the bleach and the thiosufate are irritants and can harm your skin and eyes if they come into contact with you. The thiosulfate is a basic solution and can be neutralized with weak acid (vinegar)

Homework

- Determine the results of the lab and answer the discussion questions.
- NOTE: This lab will be added to the final exam topics

NOTE: Sample Solution – see above graph (Excel is my best friend!)

- y = 1.4778 x
- y = -3.9663 x + 99
- set together and solve
- 1.4778 x = -3.9663 x + 99
- x = 18.2 mL
- mole ratio = volume ratio
- mole ratio = (18.2 mL / 6.8 mL) = 2.7 moles A / 1.0 moles B

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