Acids and Bases

[505968894]

Is a negative pH possible?

[505968894]

Can you classify acids as strong or weak from their formulas alone?

[505801516]

Also, what does amphiprotic mean?

it means that it is able to react as both an acid and a base since it can donate and accept a proton

[505801516]

Is a negative pH possible?

even though the scale is usually 0-14, it is possible for pH to be negative.

[Andrew Wang 1K]

Is a negative pH possible?

even though the scale is usually 0-14, it is possible for pH to be negative.

Considering the pH scale is a logarithmic scale, it's not possible for the value of a log to be negative. A zero on the pH scale is the log of 1, which means the concentration of H3O+ is 1.

[Mehreen_Suzaan_1A]

"How do you know if a compound is acidic or basic?"

I don't know how to reply to comments directly but for this question, I am pretty sure you need to figure out the pH level for the compound and see if it is above or below 7. Above makes it basic and below makes it acidic!

[GPena1F]

Does anyone know if we have to memorize strong acids and bases or will it be provided for us?

I believe we won't have to memorize them and we will be provided with them.

[GPena1F]

Can you classify acids as strong or weak from their formulas alone?

You can't classify acids as strong or weak from their formulas alone. However, you can memorize the strong and weak acids provided to us then recognize them from the formulas provided by the question.

[Julia Mizzi 2I]

How can you tell if a compound is acidic or basic?

If a compound is acidic, it will usually have a hydrogen. If a compound is basic, it will usually have hydroxide. However, the best way to tell would be to calculate the pH!

[GPena1F]

If a temperature is not given, can we assume we are solving at 25 degrees celcius?

Yes; 25 degrees Celsius is the standard.

[Julia Mizzi 2I]

Is a negative pH possible?

A negative pH is technically possible if the molarity of hydrogen ions is large enough, however, in most examples I believe we will only see pH values from 0-14 as that is the typical pH scale

[Julia Mizzi 2I]

How to determine the change in concentration when making the ICE table?

The change in concentration is usually represented by the variable x in the ICE tables. You would then subtract x from the reactants and add x to the products as products are being formed in the reactions.

[alyssa]

Is knowing if an acid/base is strong or weak relevant to solving any specific problems in 14B or is it just extra information?

[Julia Mizzi 2I]

Where do we find the answers to the recommended practice questions from the book?

It's in the "back matter" section of the book and then look under "odd number exercises" and scroll down to find the problem you're looking for

[Julia Mizzi 2I]

How do acids and bases relate with pH levels and substance concentrations?

Acids have a pH level below 7, while bases have a pH level above 7. Also if a solution is diluted so the concentration is less, the pH will decrease as the concentration of hydrogen ions decreases

[Cara_Holden_3A]

In which situations does an acid or base completely dissociate?

[Cara_Holden_3A]

Is a negative pH possible?

A negative pH is possible! Although I believe it’s beyond the scope of this class?

[Alison Shamoony 1G]

Also, what does amphirotic mean?

Hello, so It is basically describing an element that can donate and accept a proton and in turn will be able to react as an acid and base. Typically an amphirotic substance typically contains a hydrogen atom

[Cara_Holden_3A]

Is knowing if an acid/base is strong or weak relevant to solving any specific problems in 14B or is it just extra information?

I believe it matters in calculating concentrations after a reaction has completed since a strong base or acid will completely dissociate into its ionic components.

[Jessica_Lin_1J]

Does anyone know if we have to memorize strong acids and bases or will it be provided for us?

There should be a list provided for us.

Although Professor Lavelle provided us with a list of strong/weak acids and bases, if I remember correctly, we are still required to be able to identify them on the midterm and final.

[Jessica_Lin_1J]

Is knowing if an acid/base is strong or weak relevant to solving any specific problems in 14B or is it just extra information?

Because weak acids and bases do not completely disassociate in a reaction while strong acids and bases completely disassociate, there are certain problems we can only solve with weak acids and bases. For example, we went over what percent ionization is and how to calculate it in weak acid and base reactions. This value essentially tells us the percentage that the reaction will create the ion(s).

[Jessica_Lin_1J]

In which situations does an acid or base completely dissociate?

My TA gave us a sports analogy that I thought would be good to share, here it is:

Acid = quarterback
Base = receiver

Strong acid: good QB with high pass rate & lets go of the ball (H+)
Strong base: good receiver that holds onto the ball until touchdown (reaction)
Weak acid: bad QB with low pass rate & holds onto the ball (H+)
Weak base: bad receiver that drops the ball before touchdown (reaction)

[Alex Ottersbach]

There is a section under 14A. There are various videos and links for acids and bases in 14B though.

[Ruby Stuart 1I]

How do you know if the change in ICE is a -x or +x if given molar concentrations for all three substances?

[tristenaguinaldo]

In which situations does an acid or base completely dissociate?

Strong acids and bases dissociate completely.

[Julia Mizzi 2I]

In which situations does an acid or base completely dissociate?

I believe strong acids and bases completely dissociate while weak bases don't completely dissociate 2

[tristenaguinaldo]

How do you know if the change in ICE is a -x or +x if given molar concentrations for all three substances?

Typically, a - is used for the reactants and the + is used for the products of molar concentrations. Also, the coefficient of the change in ICE tables would be put in between the +/- and x of each substance.

[tristenaguinaldo]

What is the difference between K and Q reaction quotients. Does K only apply for reactions at equilibrium?

Q is a quantity that changes as a reaction system approaches equilibrium. K is the numerical value of Q at the "end" of the reaction, when equilibrium is reached.

[noahgraham]

In the equation where it says that pKw = pH + pOH = 14 at 25(degrees c) what does the p mean in the pKw section? And just to clarify the Kw refers to the equilibrium constant when water is involved right?

p just means to take the -log of whatever comes after it. pH would mean to take -log(H+ concentration) and the same with OH and Kw. you would be taking the -log of the Kw constant. Kw is the constant for H+ and OH+ concentrations being multiplied together.

[Prachi Roy 2K]

In the equation where it says that pKw = pH + pOH = 14 at 25(degrees c) what does the p mean in the pKw section? And just to clarify the Kw refers to the equilibrium constant when water is involved right?

p means that you're basically taking the negative log of Kw. So -log[1.0 *10^-14]=14

[Prachi Roy 2K]

Is a negative pH possible?

Yeah, I think in lecture Dr. Lavelle said it is possible when the concentration of H3O is greater than 1.0 M. However, in most biological situations, the pH range is 0 to 14.

[Prachi Roy 2K]

In which situations does an acid or base completely dissociate?

When an acid or base is classified as strong, it will completely dissociate.

[Prachi Roy 2K]

How to determine the change in concentration when making the ICE table?

So basically you add -x per mole from the initial concentrations given. For the starting condition of 0, you add x per mole. Not sure if that makes sense but its just a change of x per mole and the direction usually goes from higher concentrations to lower concentrations.

[Neha Humbe 3E]

Where do we find the answers to the recommended practice questions from the book?

If you go to the Home page of BruinLearn for this class, the answers to the practice questions are at the link called "Chemical Principles, 7th Edition, Student Solutions Manual (Fundamentals, 1-7, 9)" Hope this helps!

[705995679]

Do the weak acids not get accounted for when we calculate the K of the equation? Or does that just apply to solids?

[Emily Lee 2H]

amphiprotic means that a species can both donate or accept a proton. Water is an example, in autoprotolysis reactions.

[Hannah Fiel 2H]

Does anyone know if we have to memorize strong acids and bases or will it be provided for us?

The list of strong/weak acids and bases can be found on the class website under learning outcomes titled "List of Acids and Bases."

[Hannah Fiel 2H]

Do the weak acids not get accounted for when we calculate the K of the equation? Or does that just apply to solids?

I believe that all aqueous solutions, including weak acids/ bases are accounted for when we calculate K because they contribute to the overall concentration at equilibrium (even if the concentration is small). Only solids and liquids are discounted from the equation.

[Emily Lee 2H]

Strong acids and bases ionize fully in an aqueous solution. Weak acids and bases also ionize, but only partially and the reaction is reversible.

[KWilson_Disc_2F]

Do we need to memorize certain acids or bases or will we be told whether or not it is a strong acid or base?

I think memorizing them will certainly make these problems easier to do. The professor recently emailed a list of all the strong acids and bases and here is a link to a quizlet to study them! https://quizlet.com/_cob0nb?x=1jqt&i=40ipnb

[Karsten Wise 3D]

Does anyone know where to find the list of acids and bases we are responsible for memorizing? I'm at a loss.


EDIT: pardon me, missed the post directly above mine! Looks like there is a quizlet at https://quizlet.com/766418951/acids-and ... ds/?x=1jqt

[Luke Smith]

Hi folks, I have a quick question regarding the ICE table / quadratic equation method. I must have forgotten to write it down, what is the maximum K value from which it is acceptable to assume x is near enough to round to zero?

[Luke Smith]

Also, a secondary question also regarding the ICE table / quadratic equation process; I just wanted to double check, we ignore any negative values we get from solving the quadratic equation, correct?

[mlansing]

Can someone explain how to tell whether an approximation for concentration is valid or not? What are the parameters to check if it was okay to do?

[gracetran3d]

Lavalle sent an email out recently saying that it will be provided to us and gave a list.

Should we memorize the list?

[Luke Smith]

Do the weak acids not get accounted for when we calculate the K of the equation? Or does that just apply to solids?

Hi, I think that just applies to solids and liquids. I believe whether or not you take into account a weak acid or weak base depends on if you are trying to find Ka or Kb.

[rejoice_puente_3L]

How do you know whether a compound is an acid or a base? Following that, how do you know whether it produces OH- or H3O?

[Andrew Greenberg 2D]

Where do we find the answers to the recommended practice questions from the book?

The syllabus has all of the recommended practice problems for each section. You can find the syllabus on the class website.

[Freddie P-G 1H]

Also, what does amphiprotic mean?

Amphiprotic is when a compound is able to accept a proton and donate a proton. Basically this compound can act as both an acid and a base.

An example is water. In the presence of an acid it accepts a proton. In the presence of a base it donates a proton

[805737147]

I just had a quick question about conjugate acids and bases. I just wanted to know how we know which compound is the conjugate acid/base in the chemical reaction and also how this concept may come up when solving problems?

The question might ask you to work backwards and give you the x value for the conjugate base/acid and you have to fill in the ICE chart to find the initial concentration. I think #5 for the HW teaches you how to work backwards in this kind of problem.

[Freddie P-G 1H]

Do we need to memorize certain acids or bases or will we be told whether or not it is a strong acid or base?

We need to memorise. Here's a list: All group 1 and 2 hydroxides are strong bases, the others are weak.
HCl, HBr, HI, HClO4, HClO3, HNO3, H2SO4 are all strong acids, the others are weak

[Damin Rawlins 3B]

I was wondering on how we're supposed to know when to use either the Bronsted-Lowry Definition of an Acid/Base, and the Lewis Definition. Help would be greatly appreciated :)

[bella moore]

Question:
HClO is a weak acid ( Ka=4.0×10−8 ) and so the salt NaClO acts as a weak base. What is the pH of a solution that is 0.072 M in NaClO at 25 °C?
When I was doing this, I was confused about how to set up the equation and how they were interacting.
This is what I have so far:

I had the reaction as HClO (aq) + H20 (l) <--> ClO- + H30+ is this correct so far? (Ka)(Kb) = 1.0x10^-14
Kb = 1.0x10^-14 / 4.0×10−8
(can you do this only with water? is this only Kw?) do I need to do
Then I tried to set up an ICE table: make it pKa to pKb to Kb?
HClO ClO- H30+
I 0 .072 0 or .072
C x -x -x Where do I go from here? What is incorrect with what I am doing?
E. x. .072-x. .072-x (or -x?)

[Margreet Gawargious lecture 2 section 2H]

Will the acid and base list that Professor Lavelle provided be the only possible strong/weak acids and bases that can come up on a test, or are they simply a list of the most popular ones?

[Omaia Olivas 1C]

Where do we find the answers to the recommended practice questions from the book?

You could find the recommended practice problems on page 3 of the syllabus.

[Layla Shapouri 2L]

In the equation where it says that pKw = pH + pOH = 14 at 25(degrees c) what does the p mean in the pKw section? And just to clarify the Kw refers to the equilibrium constant when water is involved right?

p in most situation is just another way to say -log. So, for example the pH, as we know is the -log (H+). This also goes for pOH and pKw.

[Layla Shapouri 2L]

Is knowing if an acid/base is strong or weak relevant to solving any specific problems in 14B or is it just extra information?

It is helpful depending on the question. If the reaction involves a strong base or acid, then we know that the entire compound will dissociate into salt. However, when dealing with a weak acid or base, then it does not completely dissociate and we would have to calculate exactly how much dissociated in order to proceed with the problem.

[505769291]

Where do we find the answers to the recommended practice questions from the book?

They are on canvas under welcome and getting started and they are labeled "Chemical Principles, 7th Edition, Student Solutions Manual (Fundamentals, 1-7, 9)"

[Abigail S 2C]

How to determine the change in concentration when making the ICE table?

It’s basically all about understanding the reaction equation provided. You make columns for each reactant and product, besides H2O and then if it is a reactant it is most likely a -x value and with a product it is a +x value, the number (if there is one) in front of the X is determined by the equation, for example if there are 2NH3 as the reactant, then the x value will be -2x. Then the x values are added to the initial concentrations if you know them and then are plugged into the equation.

[Abigail S 2C]

When given a problem with Kb instead of Ka does this change the order in which you complete the problem or do all of the steps pretty much stay the same?

[Suraj Kulkarni 2B]

Does anyone have a list of the acids and bases we are supposed to know?

[505681302]

In the equation where it says that pKw = pH + pOH = 14 at 25(degrees c) what does the p mean in the pKw section? And just to clarify the Kw refers to the equilibrium constant when water is involved right?

Kw is the equilibrium constant for pure water and pKw comes from the equation pKw=-logKw, which helps calculate pH or pOH

[505681302]

When given a problem with Kb instead of Ka does this change the order in which you complete the problem or do all of the steps pretty much stay the same?

All steps are pretty much the same except when you get to the final steps and have to calculate either pH or OH or anything else they ask

[Maya_Panozzo_2D]

Are the pH and the pKa equal? Also, the pOH and pKb?

[Maya_Panozzo_2D]

Can you use the blank equation HA + H20 <=> H3O+ + A- for any acid problem and A- + H2O <=> HA+ + OH- for any base problem?

[Maya_Panozzo_2D]

Does anyone have a list of the acids and bases we are supposed to know?

https://lavelle.chem.ucla.edu/wp-conten ... _Bases.pdf
Lots of people have been saying that you just really need to memorize strong acids and bases and then you'll be fine.

[Maya_Panozzo_2D]

I was wondering on how we're supposed to know when to use either the Bronsted-Lowry Definition of an Acid/Base, and the Lewis Definition. Help would be greatly appreciated :)

Both are just different types of definitions of how there can be an acid or base reaction. I think both definitions are more of a conceptual idea than something that you need to know for calculating purposes.

[805737147]

Can someone explain 6D15 part b? I thought we can eliminate Cl- from the equation, but then if we consider it to be a strong acid, wouldn't the x value just be 0.055? However, that does not yield the correct answer.

[805737147]

Is a negative pH possible?

I think technically you can calculate one, but pretty sure for our class we won't have a problem that will yield a neg pH.

[Alyssa Gates 1H]

In the textbook problem 6D.9, it asks us to use the percentage deprotonation (2.4%) of benzoic acid in a 0.110 M solution to find pH and Ka.

Does it matter if we put (1-0.024)(0.110) or just (0.110-0.00264). I know it is the same answer either way but I was wondering if we should follow the expression in the ice table which is 0.110-x or do it the way in the key on canvas (which is (1-0.024)(0.110))

[sally peterson]

How can you tell if a compound is acidic or basic?

I think it might just be something you have to memorize. Dr. Lavelle gave us a list of common acids and bases and my TA told us to memorize them.

[GPena1F]

Also, what does amphiprotic mean?

Amphiprotic is the ability to respond as both an acid and a base because it can both donate and take a proton.

[GPena1F]

Are the pH and the pKa equal? Also, the pOH and pKb?

No, pH is equal to the sum of the pKa value and the log of the conjugate base concentration divided by the weak acid concentration.

[GPena1F]

In which situations does an acid or base completely dissociate?

While weak acids and bases only partially dissociate, strong acids and bases entirely do so.

[renee chowdhry 1A]

Does anyone know if we have to memorize strong acids and bases or will it be provided for us?

I believe we have to memorize it! and there are a few mnemonics which could help you memorize the strong acids! For example, one of them is So (H2SO4) I (HI) Brought (HBr) No (HNO3) Clean (HCl) Clothes (HClO4).

[Keanu Ngo 3B]

How can you tell if a salt is acidic or basic?

[Alec Villarreal 2H]

Do we need to memorize only strong acids and bases or memorize both strong and weak acids and bases?

[Rubani Chugh 2K]

What is an acid and a Base? How can you tell the difference? Have a nice day.

The pH of an acid will be less than 7 while the pH of a base will be greater than 7.
The pH of an acid is calculating by finding -log of the hydronium ion concentration in the solution. The pH of a base can be found by first calculating the pOH (-log of hydroxide ion concentration in solution). After finding the pOH, the pH an be calculated by solving 14 - pOH.

[Alec Villarreal 2H]

Do we need to memorize the list of acids and bases that the professor provided to us?

[Rubani Chugh 2K]

How can you tell if a salt is acidic or basic?

One can tell if a salt is acidic when a strong acid reacts with a weak base. A salt is basic when a strong base reacts with a weak acid. When a strong base interacts with a strong acid, the salt is neutral.

[Deivy Gonzalez 3H]

I appreciate all the help, and thanks for answering my question about the principle.

[305693278]

Lavalle sent an email out recently saying that it will be provided to us and gave a list.

He sent an email with the list but it seemed as though the list wouldn't be provided to us and we would have to memorize them. Did he specifically clarify this?

[alyona]

How can you tell if a compound is acidic or basic?

The Lewis theory states that acids accept elections and bases donate electrons.

[906023369]

Do we have to memorize what a monoprotic acid is for the test?

[906023369]

Do we have to memorize the chemical reaction for a certain element (for example: NH4Cl)?

[906023369]

Do we only approximate when the value is less than 10^-3?

[905722616]

Also, what does amphiprotic mean?

Amphiprotic just means that the molecule is able to both donate and accept a proton. Therefore it is able to react as both an ACID and a BASE

[905722616]

Do we only approximate when the value is less than 10^-3?

That's the rule of thumb that Lavelle gave in class. However, there were some problems on the Week 2 achieve homework where I applied that rule and It didn't work for me. What I've been doing now to make sure that I get the question correct is to approximate regardless of the 10^-n value and to check the percentage ionization. If it is below 5% you should be good to approximate, if it is above, stick with the quadratic formula.

[Elizabeth Park 1B]

You can determine if a compound is acidic or basic by looking at the cation and anion of the compound and seeing what they will form with water (strong/weak acid or strong/weak base). For example, if NaCN is placed in water, NaOH and HCN will form. NaOH is a strong acid while HCN is a weak base, indicating that NaCN is basic (rather than acidic or neutral).

[Elizabeth Park 1B]

How can you tell if a salt is acidic or basic?

You can determine if a compound is acidic or basic by looking at the cation and anion of the compound and seeing what they will form with water (strong/weak acid or strong/weak base). For example, if NaCN is placed in water, NaOH and HCN will form. NaOH is a strong acid while HCN is a weak base, indicating that NaCN is basic (rather than acidic or neutral).

[Elizabeth Park 1B]

Do we have to memorize what a monoprotic acid is for the test?

I believe that you should memorize what it is because there is a chance that a problem may not state a specific acid in which case you will have to just use the equation HA + H20 ⇌ A- + H3O+

[Elizabeth Park 1B]

Can you use the blank equation HA + H20 <=> H3O+ + A- for any acid problem and A- + H2O <=> HA+ + OH- for any base problem?

You can only use those equations if the base or acid is monoprotic.

[EmiD 2H]

When we are given a situation where we have to find pOH using pOH + pH = 14 to calculate one of them and the temperature is not at 25c, how do we solve it?

[EmiD 2H]

If the acid or base is not monoprotic, will we be given the dissociation equation?

[Russell Ahmed 2K]

When are we allowed to make the approximation that the initial concentration(s) of reactants don't change that much?

[Russell Ahmed 2K]

How do I know if a salt is going to affect pH?

[Russell Ahmed 2K]

Does anyone have a good mnemonic for memorizing strong acids and bases?

[Giacomo Carter 2D]

Are the answers for the homework for the textbook questions posted somewhere?

[Giacomo Carter 2D]

Do we have to memorize what a monoprotic acid is for the test?

I believe so. Although a monoprotic acid is just one that donates only one proton meaning it can only dissociate once. Although you need to know what this is most acids are monoprotic and only dissociate once.

[mlansing]

Can someone explain what a protonation state is and how to find it? Will this be something to look out for on the midterm