CHEM 01LA Lecture Notes - Lecture 3: Hydration Reaction, Copper(Ii) Sulfate, Ion
CHEM 01LA Experiment 3: Water of Hydration
●Experimental Purpose:
○The purpose of this experiment is to study the properties of hydrates, as well as
calculate their formulas
●Water of Hydration
○Water of hydration: larger amounts of water chemically bound to the cation of an
ionic salt crystal
■Water of hydration may be easily removed by heating the hydrate to a
temperature above the boiling point of water (drives the water of hydration
off)
●Dehydration reaction example
○CuCl2 * 2H2O → CuCl2(s) + 2H2O(g) at t ≥ 110℃
■Hydrated crystals: green
■Dehydrated crystals: brownish-yellow
●Hydration Terminology
○Efflorescence: hydrates that lose water to the atmosphere upon standing
■Depends on amount of water in the air (relative humidity)
○Hygroscopic: anhydrous ionic compounds that absorb water from the air or other
sources
■Deliquescence: hygroscopic compounds that can take up so much water
from the air that they dissolve in the water they absorb
●False Hydrates
○Some compounds evolve water on being heated but are not true hydrates
■Water is produced by decomposition
of the compound rather than by loss
of water of hydration
●These types of decompositions are not reversible
●Organic compounds (particularly carbohydrates)
○All ionic hydrates are water-soluble
■Generally: moles of water per mole of ionic compound is either an integer
or a multiple of ½
●Properties of hydrates to be studied:
○Identify hydrates in a group of compounds
○Observe the reversibility of the hydration reaction
○Test substances for efflorescence or deliquescence
○Determine amount of water lost by a sample of water lost by a sample of
unknown hydrate on heating
●Calculations
○Calculate the formula of the hydrate, given formula or the molar mass of an
anhydrous sample
●Important Concepts
○Hydrate: compound whose formula includes a specific number of water molecules
○CuSO4 * 5H2O: copper (II) sulfate pentahydrate
■Blue solid
■Contains five water molecules:
Document Summary
The purpose of this experiment is to study the properties of hydrates, as well as. Water of hydration : larger amounts of water chemically bound to the cation of an ionic salt crystal. Water of hydration may be easily removed by heating the hydrate to a temperature above the boiling point of water (drives the water of hydration off) Cucl 2 * 2h 2 o cucl 2 (s) + 2h 2 o(g) Dehydrated crystals: brownish-yellow at t 110 . Depends on amount of water in the air (relative humidity) Efflorescence : hydrates that lose water to the atmosphere upon standing. Hygroscopic : anhydrous ionic compounds that absorb water from the air or other. Deliquescence : hygroscopic compounds that can take up so much water from the air that they dissolve in the water they absorb sources. Some compounds evolve water on being heated but are not true hydrates.
