acid and base strengths/resonance/pH

strong acids are

fully ionized in water, there is no more reactant in solution, it completely goes to products

weak acids are

not fully ionized in solution, only partially

how do you test if something has ions in the solution

you would conduct electricity through it, ex: lightbulb. if solution has ions there will be electricity conducted, if not then the light bulb will not glow/no electricity would be conducted

you have a .1M of a strong acid and a .1M of a weak acid, which will make lightbulb glow brighter

strong acid bc its ions 100% dissociate in solution, there are more ions to carry the electricity and conduct it

dilute and concentrated doesn't tell us about

the strength of acid, concentration and dilution doesn't tell you anything about the strength. a 5m solution of weak acid and 1m solution of strong acid, you can't decide which is stronger from just that info

you have a concentrated and a dilute solution of the same acid. which makes the bulb grow more brightly

the concentrated solution would make it glow brighter bc it has a more concentrated amount of ions in there than the diluted amount

which is the strongest acid: CH4, NH3, H2O, and HF

1) check the polarity of the bond, the more polar it is, the easier it is to attract a base by interacting with its lone pair

2) to be a strong acid, you must have a conjugate base be stable, and for that, it has to be very electronegative

answer: HF, HF is a super polar bond and fluorine is extremely electronegative, it would be able to handle the extra electron

electronegativity increases:

across a row and up (closer to fluorine)

which is the strongest acid: HF HCl HBr or HI, see acid strength worksheet!!! super important and wasn't able to put whole thing on here

HI

-electronegativity can not explain strength DOWN A GROUP. down a group bond enthalpies decrease making it easier for a bond to break between an H-X within the acid the further down the group. down a group, atoms are larger, meaning the attraction between the two nucleii isn't as strong/larger electron cloud

-H-F would not be the strongest because it has the highest bond enthalpy, meaning it takes the most energy to break that bond and bc H-F are the closest in size = overlap = nucleii are closer together and since it's so strong it won't dissociate as well. this would result in a positive delta g. f^- is a small and highly charged ion that attracts h2o so there would be less entropy if F were to attract h2o to it.

-HI has the weakest bond enthalpy bc it's the lowest down the group, meaning it will dissociate the easiest in solution

explain why the delta h for HF HCl HBr and HI with water is negative / exothermic

the O-H bond is stronger

-since enthalpy is negative, you released more energy than absorbed bc the formation of the OH^- bond overrode all the energy absorbed to break the bond

the trend in entropy for HF HCl HBr is negative and decreases down till -4 at hbr. it is positive for HI and is positive 4 explain this trend for t delta s

-HI is the only one that's entropically favorable.

it is more likely for HI to break apart and dissociate completely in water than for the other compounds because their bonds strengths are stronger than HI

there is a solution, where H, hydrogen and A (a generic acid) are placed into it. only a few atoms dissociate into ions, is this a strong acid, weak acid, or neither

a weak acid

there is a solution, where H, hydrogen and A (a generic acid) are placed into it. all dissociate into ions. is this a strong acid, weak acid or neither?

strong acid

which is the stronger acid, H2O or NH3

-pick the most polar one

-and pick the one that would be most stable when a hydrogen is broken off (the most electronegative)

=h2O

which is the stronger base, NH3 or H2O

-which one would donate its electrons better?

nitrogen bc it's less electronegative than oxygen

=NH3

acid strength depends on

-the strength of the H-X bond

-the enthalpy change when added to water (strength of h-x bond and stability of x^- conjugate base)

-the entropy change when added to water

-the stability of the x^- conjugate base

write out the general reaction for H-X +H2O when x is all the halogens, like F, Cl, Br, I

H2O will be your base because oxygen is more likely to lose its electrons than the halogens and because when the halogens lose the hydrogens, they'll be the most stable

which is the strongest acid: H2O, CH3CH2OH, CH3CO2H

1) draw out lewis structure (make sure to draw them not so symmetrical lol) and then what it would look like as a conjugate base. a strong acid will have the most stable conjugate base

-CH3CO2H has two oxygens on the right side, making it a concentrated area of electronegativity, meaning that there is electron flow within the molecule to stabilize it. the electrons from the single bond w oxygen move from the single to the double bond, making the double bonded O break and create just a single bond and there is a double bond now where the single bond was/this is resonance. this shows that acetic acid is the strongest acid bc it can handle the extra electrons that it would gain in an acid-base reaction.

strong acids have

weak conjugate bases

-because it's not very reactive

the weaker the conjugate base, the

stronger the acid

strong acid means

reactive

conjugate bases can be stabilized by

resonance aka the spreading out the negative charge over several atoms like the example w acetic acid^ CH3COOH

which is a stronger base OH^- or H2O

aka which is gonna donate its electrons more readily

-OH^-

because it has a full negative charge whereas the H2O only has a partial negative on its' oxygen and will donate the electrons off its oxygen than the water would

which is a stronger base CH3 ^-, NH2 ^-, OH^- or F^-

1) draw lewis structures

2) find which one is gonna donate electrons more readily

-you want a strong base, so you want a stable conjugate acid

the least electronegative (one that is least likely to hold onto its electrons) is carbon, has a CH3 and a lone pair. it will not react as an acid, will be a stable acid (weak acid) so CH3^- is a strong base

if you add a strong acid (really reactive acid) + strong base (really reactive base) what will you produce

stable products, weak acid and weak base

if you add a strong acid (really reactive acid) + strong base (really reactive base) would you predict that there would be more reactants or products for this reaction?

look at the acids and bases on both sides to predict this...?

in acid-base reactions, which side is going to have more, reactants or products?

-if you react a strong acid and strong base, and they yield a weak acid and weak base, the reactants dissociate 100% meaning its making 100% product.. they are much more reactive and will drive the reaction towards more products.

-if you have a stronger conj acid and base (products) they react much more than the reactants do so it drives the reaction to the reactants side (making more reactants)

What is the auto ionization of water? *****she said to know all this******

where water reacts with itself.

-at 25 degrees celsius the concentration of each ion is 1 times 10^-7 M

**KNOW THIS***

reactivity changes with

temperature

[H3O^+] =

[OH^-]

what percentage of water molecules in pure water are ionized at 25 degrees celsius (is asking what percentage of water are products)

**remember water at 25 degrees celsius has an ion concentration (of hydronium) of 1 x 10^-7 M

1) part/whole times 100 to get the percent

1 x 10^-7 M/55.5M bc 55.5 M is the concentration of water

= 1.8 x 10^-7 %

in pure water [H3O^+] = [OH^-] = 1 x 10^-7 M

therefore [H3O^+][OH^-] =

1 x 10^-14

if your pH is 3, do you have more hydronium or hydroxide

hydronium bc that's in acidic solutions, hydroxide is basic

if [H3O+] = 1 x 10^-1 M, then what is the [OH-]

-also what is the pH?

-which is the greater concentration? what does this mean

1) since [H3O^+][OH^-] =1 x 10^-14, plug in the conc of hydronium and then solve for hydroxide

(1 x 10^-1M)x = 1 x 10^-14

=1 x 10^-13 M

2) pH=-log[H3O+]

equals 1

3)great conc is the hydronium, meaning it's more acidic

in pH, the p means

negative log (of whatever)

pH =

-log[H3O+]

if [OH-] = 2.6 x 10^-2 M what is the conc of hydronium

it is 3.8 x 10^-13 M

if [OH-] = 2.6 x 10^-2 M what is the conc of hydronium, what is the pH?

1) get conc of hydronium

= 3.8 x 10^-13 M

2) pH = -log[hydronium]

=12.4 meaning this would be basic bc ur hydroxide conc is much greater

the pH of .10 M HCl is 1.00 but .10 M of acetic acid is 2.89. why

the HCl dissociates completely bc it's a strong acid, acetic acid is not as strong

[hydronium] =

10^-pH

what is the concentration of hydronium if HCl solution has pH of 1 and is 0.1 M. what is the percent ionization?

1)[hydronium] = 10^-pH

10^-1

= 0.1 M

2)(part/whole) times 100

0.1/0.1 x 100= 100%, it is a strong acid

0.1 M of acetic acid has a pH of 2.89. what is the percent ionization for acetic acid: are there more reactants or products?

1) get the concentration of hydronium:

10^-2.89 = 0.00128825 M

2) 0.00128825 M/0.1 M x 100 = 1.28%

-there are more reactants present bc it does not dissociate very well, meaning it's a weak acid

Here are two different acidic solutions:

(1) a solution with a pH of 2.30

(2) a solution with a pH of 1.30

Can you predict which acidic solution contains the stronger acid? Explain your reasoning.

you need to know the molarity of the solution to be able to calculate the percent ionization. percent ionization tells you how much a solution has dissociated, so if one dissociates more than the other, that means that it is stronger acid.

If the solution with the pH of 2.30 had a concentration of

0.05 M, what is the percent ionized for the acidic solution?

1) calc hydronium concentration

[hydronium] = 10^-pH

= 0.005011872 M

2) % ionization is (part/whole) x 100

(0.005011872 M/0.05 M) x 100 = 10.0%

Draw a particulate (molecular level) representation of the

solution mixture in Question 2. Do not include water molecules in your drawing.

should look like a couple atoms have ionized but most are still stuck together with their molecules, 10% of the entire solution can be broken up into ions, means your product should be 10% dissociated products and 90% reactants. so if you had 10 product molecules 1 of them would be dissociated and the other 9 would still be reactant

what would the arrow for this reaction look like?

it would be the equilibrium arrows bc it did not dissociate completely

Using the data given in Question 2 along your responses in

Questions 2 and 3, what can you predict about the strength

of the acid? How do you know?

the acid is not that strong because it doesn't dissociate very much. since it doesn't dissociate completely, that means it's not a strong acid.

If the solution with the pH of 1.30 had a concentration of 0.05M, what is the percent ionized for the acid solution?

1) calc the [hydronium]

10^-1.30= 0.050118723 M

2) calc the percent ionization, (part/whole) x 100

0.050118723 M / 0.05 M x 100 = 100%

what would the arrow for this reaction look like?

it would only go one way (wouldn't be equilibrium arrows bc it dissociates completely)

Draw a particulate (molecular level) representation of the

solution mixture in Question 5. Do not include water molecules in your drawing.

the entire acid molecule has been ionized, aka it is fully broken up into ions bc there is a 100% ionization. so if you had 10 molecules, then you have 10 of one atom and 10 of the other atom

Using the data given in Question 5 along your responses in

Questions 5 and 6, what can you predict about the strength

of the acid? How do you know?

this acid is strong bc it dissociates completely in solution

what do you do to determine what is a strong acid and weak acid?

through percent ionization, just bc something has a low pH doesn't mean shit

Now use your answers from Questions 4 and 7 to reflect back on your answer from

Question 1. How do your answers compare? Redo Question 1 if needed.

Now

use your answers from Questions 4 and 7 to reflect back on your answer from

Question 1. How do your answers compare? Redo Question 1 if needed.