Experiment 5: Percent Water in Hydrated Salt

Questions and Answers

If the original sample is unknowingly contaminated with a second anhydrous salt, will the reported percent of water in the hydrated salt be too high, too low, or unaffected? Explain.

too low

What error occurred when the crucible was contaminated with cleaning oil before measuring its mass? Is the mass of the anhydrous salt reported as being too high or too low? Explain.

too low

If the hydrated salt is overheated and some mass turns into gas, will the reported percent water in the hydrated salt be reported too high, too low, or unaffected? Explain.

too high

Study Notes

Experiment Errors and Their Effects on Reported Results

Contamination of original sample with a second anhydrous salt leads to an underestimation of percent water in hydrated salt.
Additional mass from the contaminant increases the overall mass used in the percent calculation, lowering the fraction's value.

Impact of Cleaning Oil on Mass Measurement

Presence of cleaning oil on the crucible introduces measurement error.
The mass of the anhydrous salt appears too low because the oil is mistakenly accounted for, suggesting an inaccurately elevated initial mass.
The burning off of the oil during heating causes a loss in apparent sample weight, compounding the error.

Effect of Thermal Decomposition on Percent Water Calculation

Overheating of hydrated salt results in thermal decomposition, creating gas as a byproduct.
The loss attributed to water is overestimated as a part of the mass loss is incorrectly assumed to be solely from water.
This leads to a reported percent of water in the hydrated salt that is too high since some mass lost is due to gas generation from the decomposition of the solid.

Description

Test your knowledge with flashcards on the percent water in a hydrated salt. Explore the implications of contamination on percent calculation and understand fundamental concepts in experimental chemistry.