Which of the following observations give evidence that a crystal is a hydrate? O
ID: 903766 • Letter: W
Question
Which of the following observations give evidence that a crystal is a hydrate? One or more answers may be correct.
Heating the crystal results in a decrease in mass which matches the expected mass for waters of hydration.
Recalculating the percent yield of the hydrated crystals using the molecular weight of the hydrated form results in a percent yield well below 100%.
Since the crystals were filtered from an aqueous solution, they are wet and must therefore be a hydrate.
On heating the crystals in a test tube over a bunsen burner, a clear liquid is noticed near the top edge of the test tube.
Adding water to crystals which have been heated results in the color returning to that of the crystals before heating.
The number of water molecules in the hydrated crystals is calculated from the mass lost on heating. This matches the expected number based on a google search.
a.Heating the crystal results in a decrease in mass which matches the expected mass for waters of hydration.
b.Recalculating the percent yield of the hydrated crystals using the molecular weight of the hydrated form results in a percent yield well below 100%.
c.Since the crystals were filtered from an aqueous solution, they are wet and must therefore be a hydrate.
d.On heating the crystals in a test tube over a bunsen burner, a clear liquid is noticed near the top edge of the test tube.
e.Adding water to crystals which have been heated results in the color returning to that of the crystals before heating.
f.The number of water molecules in the hydrated crystals is calculated from the mass lost on heating. This matches the expected number based on a google search.
Explanation / Answer
a. Heating the crystal results in a decrease in mass which matches the expected mass for waters of hydration. true, since mass of water evaporates
b. Recalculating the percent yield of the hydrated crystals using the molecular weight of the hydrated form results in a percent yield well below 100%. true, since mass decreses so final mass is less than initial mass so % yyield must decrease
c. Since the crystals were filtered from an aqueous solution, they are wet and must therefore be a hydrate. false, this is humidity + water, hydrate is water attached ot the molecules
d. On heating the crystals in a test tube over a bunsen burner, a clear liquid is noticed near the top edge of the test tube. true, which is the evaporation of water
e. Adding water to crystals which have been heated results in the color returning to that of the crystals before heating. true, since they will hydrate, so they change color for th ehydrated molecules
f . The number of water molecules in the hydrated crystals is calculated from the mass lost on heating. This matches the expected number based on a google search.true, via stoichiometric ratio of moles of water per mol of salt
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.