Questions and Answers
What are the reactants in the experiment?
How does the loss of precipitate affect the reported percentage of the limiting reactant in the salt mixture?
The reported percentage will be less because of the lost precipitate.
How is the limiting reactant determined in the experiment?
Once you filter the solution, you centrifuge it and take out the supernatant.
What does the expression, 'digesting a precipitate' mean?
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If the step for digesting the precipitate were omitted, what would happen to the reported 'percent limiting reactant'?
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What will happen to the mass of the limiting reactant due to accidental water on the filter paper?
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Will the reported percent of the limiting reactant be too high or too low if some precipitate passes through the filter?
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What will occur if excessive quantities of wash water are added to the CaC2O4 H2O precipitate?
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What happens if the precipitate is not completely air-dried when its mass is determined?
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How will a drying oven set incorrectly affect the reported percent by mass of the limiting reactant?
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What dilemma might arise if two volumes of solution are withdrawn before the precipitate has settled?
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What would happen if a reagent bottle labeled 0.5 M NaCl was used instead of 0.5 M CaCl2?
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Study Notes
Experiment Overview
- Reactants used: Calcium Chloride Dihydrate (CaCl2 x 2H2O) and Potassium Oxalate Monohydrate (K2C2O4 x H2O).
- Limiting reactants are determined through filtration and centrifugation processes.
Precipitate Loss Impact
- Loss of CaC2O4 x H2O precipitate through filtering leads to an underestimation of the limiting reactant's percentage.
- Small particle size of the precipitate causes some to pass through filter paper.
Digesting Precipitate
- "Digesting a precipitate" refers to heating it to 75°C for 15 minutes, promoting the formation of larger crystals for efficient filtration.
- Omitting the digestion step results in a lower reported percent of limiting reactant due to inefficient filtering.
Filtering Techniques
- Adding water to properly folded filter paper before weighing leads to inaccurately low mass readings of the limiting reactant post-drying.
- Excessive washing of CaC2O4 x H2O precipitate with water results in increased dissolution, yielding a lower reported mass of the chemical.
Impact of Dampness
- If the CaC2O4 x H2O precipitate isn't completely dried before mass determination, the reported mass will be artificially high due to residual water weight.
- Missettings in drying oven temperatures can also cause incorrectly reported high mass values if the precipitate isn't entirely dry.
Experiment Errors
- If multiple volumes of solution are withdrawn before precipitate settling, it becomes difficult to assess which reactant is in excess, complicating the experiment's outcome.
- Substituting the correct reagent (0.5 M CaCl2) with the wrong one (0.5 M NaCl) impairs the ability to identify excess reactants, since both Ca2+ and C2O4^2- will be present in the mixtures.
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Description
Explore the chemistry behind the precipitation of Calcium Oxalate from Calcium Chloride Dihydrate and Potassium Oxalate Monohydrate. This quiz covers topics like limiting reactants, the impact of precipitate loss, and filtering techniques. Test your understanding of the steps involved in this critical laboratory experiment.
