AQUEOUS SOLUTIONS Section 17.3. After reading Section 17.3, you should know: The meaning of likes...
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Transcript of AQUEOUS SOLUTIONS Section 17.3. After reading Section 17.3, you should know: The meaning of likes...
AQUEOUS SOLUTIONS
Section 17.3
After reading Section 17.3, you should know: The meaning of “likes dissolve likes” and
how to determine which compounds will dissolve into each other
The difference between strong, weak and non-electrolytes
The difference between hygroscopic and deliquescent substances
Solvent vs Solute
Aqueous Solutions – water samples containing dissolved substances
Solvent – the substance doing the dissolving
Solute – the substance being dissolved
Example of an aqueous solution = salt water Solvent = water Solute = salt
Review: Ionic and Covalent
Ionic comounds = metal + nonmetal Held together by ionic charges
Polar Covalent molecules = 2 or more nonmetals Have a slight charge due to electronegativity
differences
Nonpolar Covalent molecules = 2 or more nonmetals Do not have a charge because the shape of the
molecule cancels the electronegativity differences out
“Likes Dissolve Likes” Ionic compounds and polar compounds will
dissolve in other ionic and polar compounds Ionic compounds have a full charge and polar
compounds have a slight charge, so the charges are attracted to each other.
Nonpolar compounds will only dissolve in other nonpolar compounds
Salt will dissolve in water Salt is ionic, water is polar
Oil and water do not mix Oil is nonpolar and water is polar
Solutions
Solutions are homogenous mixtures
Solvation – the process that occurs when a solute dissolves
Example: salt dissolving in water Salt is an ionic compound, water is a polar
molecule Animation of salt water and the interactions
between the molecules
Electrolytes and Nonelectrolytes Electrolytes – compounds that conduct
an electric current in aqueous solution or the molten state All ionic compounds are electrolytes
Nonelectrolytes - compounds that do not conduct an electric current in aqueous solution or the molten state
Strong electrolyte – when a substance is dissolved and almost all of the solute molecules separate into ions
Weak electrolytes – when a substance is dissolved and only a fraction of the dissolved solute separate into ions
Table 17.3 on page 485
Water of Hydration
Water of hydration is the water contained in a crystal
Hydrate – a compound containing water Example: copper (II) sulfate pentahydrate
CuSO4*5H2O
Table 17.4 on page 486
Effloresce – process that occurs when a hydrate has a vapor pressure higher than that of water vapor in the air
Hygroscopic – substances that remove water from the air Have low vapor pressure Used as desiccants or drying agents
Deliquescent – compounds that remove a sufficient water from the air to dissolve completely and form solutions When a substance has a lower vapor
pressure that that of the water in the air Example: solid NaOH pellets – react with
moisture from the air and will “melt” over time
After reading Section 17.3, you should know:
The meaning of “likes dissolve likes” and how to determine which compounds will dissolve into each other
The difference between strong, weak and non-electrolytes
The difference between hygroscopic and deliquescent substances