BIOL 1406
PreLab 3.1
What is dissociation?
A Note about Scientific Notation Scientists generally use a system referred to as “Scientific
Notation” to express very large or very small numbers.
Because it is not possible to enter superscripted exponents (e.g. 10^{-7} ) in the answer boxes that appear in this Lab Manual and in the Blackboard Quizzes, you must enter answers with exponents using the last method shown, i.e. using the symbol "^" to mean "raised to the power of." This method will also be used when hints or answers are shown in the pop-up boxes. Special Note: On all Blackboard quizzes, when you enter answers with exponents, you must follow these 2 rules: (1) use the "^" symbol to mean "raised to the power of", and (2) omit all spaces between all elements in the expression, including units. The reason is that Blackboard grades your answer based on an exact match with the correct answer. If the correct answer is listed as 3.4x10^4cm^3 and you enter a variation such as 3.4 x 10^4 cm^3 or 3.4x 10 ^ 4 cm^ 3 or any other combination that includes spaces, Blackboard will grade your answer as WRONG! |
The chemistry of life is based largely on the chemistry of
water. When ionic or polar solutes are mixed with water, the water molecules
(which are polar) attract them and may pull them apart into oppositely charged
ions. This process is called dissociation. In fact, water molecules may even
pull other water molecules apart to produce oppositely charged hydrogen ions
(H^{+}) and hydroxyl ions (OH^{-}).
Because water dissociates into one H^{+} and one OH^{-}, pure water always has the same concentration of H^{+} and OH^{-}, which turns out to be 1 x 10 ^{-7} M:
NOTE: The brackets indicate “the concentration of” whatever is inside the brackets.
Because of this relationship, for any aqueous solution it is possible to determine the concentration of OH^{-} if one knows the concentration of H^{+} (or vice versa). Furthermore, it means is that as [H^{+}] increases [OH^{-}] must decrease and, of course, the opposite is true as well. |
YOUR TURN | ||
Each water molecule that dissociates produces | Hint | Check your answer. |
In pure water, [H^{+}] = | Hint | Check your answer. |
In all aqueous solutions, [H^{+}] x [OH^{-}] = | Hint | Check your answer. |
If the [H^{+}] of an aqueous solution equals 1 x 10^{-3} M, then [OH^{-}] = | Hint | Check your answer. |
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