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Chapter 15 Section 15.2. Homogeneous Aqueous Systems. Think-Pair-Share. Explain why you must be extremely careful when using electricity near a swimming pool. Solutions. Aqueous Solution -Water that contains a dissolved substance. 2 Parts to a solution:

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Chapter 15 section 15 2

Chapter 15Section 15.2

Homogeneous Aqueous Systems


Think pair share
Think-Pair-Share

  • Explain why you must be extremely careful when using electricity near a swimming pool.


Solutions
Solutions

  • Aqueous Solution-Water that contains a dissolved substance.

  • 2 Parts to a solution:

    • Present in the smallest amount - Solute

    • Solvent - Present in the larger amount

  • Solvent dissolves the Solute.


Solutions1
Solutions

  • Are Solvents and Solutes found in the liquid state only?

  • Gas Solutions

    • The air we breathe- Oxygen and Nitrogen

    • Carbon Dioxide mixed with your liquid soda

  • Solid Solutions

    • Nickel Coin- Copper and Nickel

    • Sterling Silver- Silver and Copper

  • Can you name any?


Solutions2
Solutions

  • Homogeneous mixtures- nothing settles out when left standing

  • Solute particles are very…very small.

    • Less than 1nm = 10 -9 m

  • What would happen if we tried to filter a homogeneous solution through filter paper? Could you separate the solute from the solvent?


Solutions3
Solutions

  • Substances that dissolve most readily in water are…

    • Ionic Compounds

    • Polar Covalent Compounds

  • Polar molecules dissolve in Polar molecules.

  • Nonpolar covalent molecules such as oils, fuels, and grease dissolve in Nonpolar covalent molecules.


The solution process
The Solution Process

  • A water molecule is polar, with a partial negative charge on the oxygen atom and partial positive charges on the hydrogen atoms.

  • As individual solute ions break away from the crystal, the negatively and positively charged ions become surrounded by solvent molecules and the ionic crystal dissolves.


The solution process1
The Solution Process

  • The process by which the positive and negative ions of an ionic solid become surrounded by solvent molecules is called solvation.



Electrolytes
Electrolytes dissolves like

  • An electrolyte is a compound that conducts an electric current when it is in an aqueous solution or in the molten state.

  • All ionic compounds are electrolytes because they dissociate into ions.




Electrolytes1
Electrolytes flow between the two electrodes that are immersed in the

  • Not all electrolytes conduct electric current to the same degree

  • In a solution that contains a strong electrolyte, all or nearly all of the solute exists as ions. Ex: Sodium Chloride

  • A weak electrolyte conducts an electric current poorly because only a fraction of the solute in the solution exists as ions.

  • Ex: Acetic Acid



  • Pickles contain table salt. Why can electric current flow through a pickle, causing it to glow?

  • Electrolytes conduct an electric current when they are in an aqueous solution. Table salt, or NaCl, is a strong electrolyte. The water and salt in the pickle form a solution that conducts an electric current. The electric current causes the pickle to glow.




Thumbs up thumbs down
Thumbs Up…Thumbs Down electricity near a swimming pool.

  • All Solutions are conductors of electricity.

  • Degree of electrical conductivity is directly related to kinetic energy.

  • Ionic compounds conduct electricity because they contain ions.


Hydrates
Hydrates electricity near a swimming pool.

  • A compound that contains water of hydration is called a hydrate.

  • The dot is not a multiplication sign.

  • It connects the compound to however many water molecules are present.


Hydrates1
Hydrates electricity near a swimming pool.

The forces holding the water molecules in hydrates are not very strong, so the water is easily lost and regained.



Let s test our knowledge
Let’s test our knowledge… solution of cobalt(II) chloride and then dried is blue in color (anhydrous CoCl2).

  • Pg. 510 #49

  • Pg. 281 Chart 9.4


To determine what percent by mass of a hydrate is water
To determine what percent by mass of a hydrate is water: solution of cobalt(II) chloride and then dried is blue in color (anhydrous CoCl2).

  • First determine the mass of water in one mole of hydrate.

  • Then determine the molar mass of the hydrate.

  • The percent by mass of water can be calculated using the following equation:


Finding the percent by mass of water in a hydrate
Finding the Percent by Mass of Water in a Hydrate solution of cobalt(II) chloride and then dried is blue in color (anhydrous CoCl2).

  • Pg. 500 #8

  • Analyze -List the known and the unknown

  • To determine the percent by mass, divide the mass of water in one mole of the hydrate by the molar mass of the hydrate and multiply by 100%.


Let s test our knowledge1
Let’s test our knowledge… solution of cobalt(II) chloride and then dried is blue in color (anhydrous CoCl2).

  • Pg. 512 #89 d and e



Test our knowledge
Test our Knowledge… solution of cobalt(II) chloride and then dried is blue in color (anhydrous CoCl2).

  • What property of all ionic compounds make them electrolytes?

  • Why do hydrates easily lose water when heated and regain water when exposed to moisture?

  • Identify the solvent and the solute in vinegar, a dilute aqueous solution of acetic acid.


Due friday
Due Friday solution of cobalt(II) chloride and then dried is blue in color (anhydrous CoCl2).

  • Online assignment calculating % by mass.


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