ph , acids and bases
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pH , Acids and Bases. Pg 164-165. pH. Reminder: Water is held together by ___________________ bonds. These are relatively __________ bonds. These bonds are constantly _________ and _____________. Water molecules can naturally break apart. This is called the dissociation of water . - PowerPoint PPT PresentationTRANSCRIPT
pHReminder: Water is held together by
___________________ bonds.These are relatively __________ bonds.These bonds are constantly _________ and
_____________.Water molecules can naturally break apart.
This is called the dissociation of water.
Acids, Bases and pHOne water molecule in 550 million
naturally dissociates into a Hydrogen Ion (H+) and a Hydroxide Ion (OH-)
Hydrogen Ion Hydroxide Ion Acid Base
H2O H+ + OH-
The pH Scale
**Some compounds form acids or bases
Scientists use something called the pH scale to measure how acidic or basic a liquid is
The scale looks at the concentration of positively charged hydrogen ions (H+) in a solution vs. the amount of negatively charged hydroxide ions (OH-)
The scale goes from values 0 through 14.
Brain pop
Acids
Tastes sour Corrodes metals
• An acid releases hydrogen ions when it dissolves in water.
- High H+ concentration- Low OH- concentration- pH less than 7
Summary! If you have an ionic compound and you put it in
water, it will break apart into two ions.If one of those ions is H+, the solution is acidic. If one of the ions is OH-, the solution is basic.
There are other ions that make acidic and basic solutions, but we won't be talking about them here.
NeutralPure water contains small, but equal
amounts of ions: H+ and OH-On the pH scale the number is 7
Acids vs BasesAcids: Anything that dissolves in water and
adds H+. Bases: Anything that dissolves in water and
adds OH- ions.
BuffersBuffer - mixtures that can react with acids or
bases to prevent major pH changes.
Buffered aspirin has a coating on it to prevent the acids in your stomach from dissolving it right away.