Shows how water ionizes to form hydronium and hydroxide ions
Gives the ionization equation for water
Defines Kw and shows the Kw expression
Defines neutral, acidic, and basic solutions
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0:00water is usually thought of as a
0:05nonconductor however very sensitive
0:07devices can detect some conductivity and
0:10water no matter how period is even very
0:14pure distilled water contains some ions
0:16why is this so in any sample of pure
0:20water almost all of the water molecules
0:22remain as neutral water molecules and
0:24don't react chemically with each other
0:27however about two out of every five
0:29hundred and fifty six million water
0:31molecules will react chemically with
0:34each other will show two of them here
0:36but they're bonding and non-bonding
0:38electrons
0:40the purple one will act as an acid and
0:43the blue one will act as a base
0:46the hydrogen atom breaks away from the
0:49water on the left and leaves it shared
0:51electron behind
0:53because it has lost an electron requires
0:56a positive charge becoming an H+ ion or
0:59proton
1:01because the o.h is gained an electron it
1:04requires a negative charge and it's
1:06called the hydroxide ion
1:09with the formula or h minus the proton
1:12moves to a nonbonding electron pair on
1:15the other water molecule will change its
1:18color to blue
1:19the positive charge is now distributed
1:21over the whole iron instead of just
1:24being on the H that it came with
1:26this is now a hydronium ion with the
1:29formula h3o plus
1:33the process can be summarized by an
1:35equation when a proton is transferred
1:38from one water molecule to another the
1:41water on the Left gains a proton to
1:43become a hydronium ion and the water on
1:46the right loses a proton to become a
1:48hydroxide ion
1:50however when a hydronium ion in water
1:52encounters a hydroxide ion the reverse
1:55reaction can also occur where a proton
1:58is transferred from the hydronium ion to
2:01the hydroxide
2:03forming two molecules of water because
2:06both the forward and reverse reactions
2:08continuously occur this is an
2:11equilibrium so we use a double arrow
2:13here instead of writing these two
2:16separate water molecules we can combine
2:18them to show them simply as two water
2:21molecules
2:23remove this arrow over a bit this
2:26equation is very important equation to
2:28know it's called the ionization of water
2:31equation
2:32sometimes it's called the self
2:34ionization of water because water acts
2:37as both the acid and the base in
2:40chemistry 12 we refer to it simply as
2:43the ionization of water
2:45at a normal room temperature of 25
2:47degrees the reactant liquid water is
2:50highly favorite to illustrate this we
2:53show there's more reactants and products
2:56the relative sizes of the letters here
2:58are very qualitative and nowhere near to
3:01scale the concentration of hydronium and
3:04hydroxide ions are only about two
3:06billions that of water
3:09the KQ expression for this reaction is
3:11equal to the concentration of hydronium
3:13times the concentration of hydroxide
3:16because the water is a liquid it is not
3:19included in the KQ expression
3:22because this equilibrium constant is
3:24specifically concerned with water we
3:27change the symbol from KQ to kW kW is
3:32called the ionization constant of water
3:35the value for KW his
3:38temperature-dependent at 25 degrees the
3:41value is 1 times 10 to the negative 14
3:43is very important to remember the value
3:47of K W is 1 times 10 to the negative 14
3:50only at 25 degrees celsius and no other
3:54temperature
3:56but KW is always equal to the
3:58concentration of hydronium times the
4:00concentration of hydroxide at any
4:03temperature for which water is in the
4:05liquid state because all equal solutions
4:08contain water and all water ionizers to
4:11form some hydronium and hydroxide ions
4:14we know that all aqueous solutions
4:17contain some hydronium and some
4:19hydroxide ions by definition for any
4:22aqueous solution if the concentration of
4:25hydronium is equal to the concentration
4:27of hydroxide the solution is set to be
4:30neutral and if the concentration of
4:32hydronium is greater than the
4:34concentration of hydroxide the solution
4:37is set to be acidic and if the
4:39concentration of hydronium is less than
4:41the concentration of hydroxide solution
4:44is set to be basic these are the
4:47definitions will use for neutral acidic
4:50and basic solutions you must make sure
4:52that you know these
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