Data Sheet identification code of unknown c mass of crucble plus sample, g mass
ID: 560300 • Letter: D
Question
Data Sheet identification code of unknown c mass of crucble plus sample, g mass of empty crucible, g 100g mass of hydrate sample, g mass of crucible and sample: after first heating and cooling.g after second heating and cooling. g after third heating and cooling. 9 mass of water lost, g mass percent of water in sample, % formula of anhydrous salt molar mass of anhydrous salt, g mor mass of anhydrous salt, number of moles of anhydrous salt -3 remaining in the crucible, mol -2 number of moles of water lost, mol average number of moles of water per mole of hydrate, mol formula of hydrate Cal C on ANAL 479/Determining the Formula of an lonic HydrateExplanation / Answer
Ans. Mass of water lost = 28.25 g – 27.62 g = 0.63 g
Choose maximum loss in mass of water.
# Mass of dried salt = 1.02 g – 0.63 g = 0.39 g
# Molar mass of salt Na2C4H4O6 = 194.051696 g/ mol
Moles of salt in sample = Mass of dried salt / Molar mass
= 0.39 g / (194.051696 g/ mol)
= 0.0020098 mol
# Moles of water lost = Mass of water lost / Molar mass of water
= 0.63 g / (18.01528 g/ mol)
= 0.034970 mol
# Average moles of water per mol anhydrous salt =
Moles of water lost/ Moles of dried salt
= 0.034970 mol / 0.0020098 mol
= 17.4 mol
= 17.0 mol (nearest whole number)
That is, there are 17 moles of H2O per mol anhydrous salt.
So,
Formula of salt = Na2C4H4O6.17H2O
Note: moles of “hydrate” salt can’t be determined before that of empirical formula of the hydrated salt because we won’t know the molar mass of hydrated salt. So, calculating the moles of hydrated salt in earlier step (before we have established the formula of hydrated salt) is NOT feasible.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.