Zumdahl%20Chapter%204%20lecture%20slides%20sp08

Zumdahl%20Chapter%204%20lecture%20slides%20sp08 - CHAPTER 4...

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1 CHAPTER 4 z Some Types of Chemical Reactions & Solution Stoichiometry 2 Aqueous Solutions: An Introduction z Solution is a mixture of two or more substances dissolved in another. Solute is the substance present in the smaller amount. Solvent is the substance present in the larger amount. In aqueous solutions, the solvent is water. z The concentration of a solution defines the amount of solute dissolved in the solvent. The amount of sugar in sweet tea can be defined by its concentration. 3 Aqueous Solutions: An Introduction z An aqueous solution is composed of a solute (either solid, liquid or gas) that has been dissolved in water (the solvent). z The process of dissolving substances in water is energetic and requires an interaction between the dipoles of water and the charges on the solute particles. 4 Aqueous Solutions: An Introduction z This process of dissolving a solute in water is called hydration . z An example would be the hydration of an ionic salt that has been dissolved in water. The partial positive and partial negative charges on water molecules interact with the positive and negative charges on the ionic crystal. The result is that water causes the crystal to break up into individual cations and anions. 5 Figure 4.2: Polar water molecules interact with the positive and negative ions of a salt, assisting with the dissolving process. 6 Aqueous Solutions: Electrolytes Electrolytes – substances that conduct electricity when dissolved in water . z Strong electrolytes conduct electrical current very well. z Weak electrolytes conduct electrical current poorly. z Nonelectrolytes do not conduct electrical current.
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7 Aqueous Solutions: Electrolytes The number of ions in the solution determine the strength of electrolytes. z Salts that dissociate in water provide ions that are capable of carrying electrical current and are strong electrolytes . z Salts that do not dissolve in water do not provide the necessary ions needed to carry electrical current and are nonelectrolytes . 8 Aqueous Solutions: Electrolytes A soluble substance is another way of describing a substance that has dissolved in water. z Many substances will dissolve by hydration of the entire molecule rather than being broken into ions. We refer to these substances as soluble nonelectrolytes . z Many substances will dissolve by hydration of the entire molecule and will also form a few ions. We refer to these substances as soluble weak electrolytes. 9 Aqueous Solutions: Electrolytes z Strong acids and strong soluble bases provide ions that are capable of carrying electrical current and are strong electrolytes . z Weak soluble acids do not provide enough ions that are capable of carrying electrical current and are weak electrolytes .
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This note was uploaded on 02/24/2010 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas at Austin.

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Zumdahl%20Chapter%204%20lecture%20slides%20sp08 - CHAPTER 4...

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