# AP Chemistry – Lab 04 – Ratio of Reactants

Friday, September 30 – Lab Notes

The lab is an example of the stoichiometry of a reaction in solution [Instructions]. 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.
- All of the data will be combined into one spread sheet shared through Google Docs [LINK]. You must enter your data into this for all of the class to use. Your lab report will depend on using everyone’s data.
- Be mindful fo 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)

For Monday, please find the results for the lab and answer the discussion questions.

NOTE – SUNDAY EVENING

Solution using class data (See graph above)

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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