Chem exam 2 chapter 16

What is an Arrhenius acid?

What is an Arrhenius base?

Arrhenius acid = Increases H+ conc. in solution

Arrhenius base = Decreases H+

Hydronium is same as proton

H3O and H+ yes
H+ and H2O = H3O

Whats important to note about id’ing strong vs weak acids?

Strong acids go to completion with —> arrow

weak acids don’t, they’re reversible with ←—> arrow

Given the same # of initial moles of a Strong acid and a weak acid, which will produce more hydronium H3O+ ions?

Strong acid will produce significantly more hydronium ions

What are the 7 strong acids and which ones sometimes considered a weak acid?

1. HClO₄

2. HClO₃ - sometimes a WA

3. H₂SO₄

4. HNO₃

5. HCl

6. Hbr

7. HI

What are the strong bases?

1. Ba(OH)₂

2. Sr(OH)₂

3. Ca(OH)₂

4. CsOH

5. RbOH

6. NaOH

7. KOH

8. LiOH

(Bsc)² CRNKL

bitch crinkl

What’s a very common example of a weak base?

Anything that is a derivative of NH₃ , so NH_3, CH₃NH2, or anything that has a N surrounded by H’s or CH’s

• weak bases don’t contain OH, but when they ionize they produce OH by taking H+ from water so remember that

whats rule for weak bases just like weak acids

won’t ionize completely, reversible and at EQ

Given same number of moles of a dissolved strong base, and a dissolved weak base, which will produce more hydroxide ions?

A strong base

What is a bronsted acid?

What is a bronsted base?

Bronsted acid is a proton donor that releases H+

Bronsted base is a proton acceptor that makes bonds with H+

bronsted acid + base example

Why is water unique under the bronsted base definition

If H₂O gets paired with a strong base, it’ll act as an acid

If H2O gets paired with a strong acid, it’ll act as a base

This makes it amphoteric

What’s acid and base strength?

What’s relationship?

acid strength = extent acid reacts with water to form hydroniums or H+ ions

base strength = extent base interacts with water to form ions

The stronger the weak acid or base, the weaker its conjugate base or acid

The weaker the weak acid or base, the stronger its conjugate base or acid

A solution of water is neutral because it contains an equal concentration of

Hydronium (H3O) and Hydroxide (OH-) ions

1. ID if it’s a strong acid or base. If it starts with a H it’s an acid.

2. ID if it’s a strong base,

3. Write out the equation with your molecule reacting with water, that will make it make more sense,

4. When you write out the bases, the ones that produce the MOST hydoxide (OH) will produce the least hydronium (H3O ions)

5. A weak base > strong base for producing H3O

Most Hydronium

Strong acid > Weak acid > weak base > strong base (with less moles) > strong base (with more moles, i.e (OH)2)

For C, this is finding pH given a base

How to calculate pH of a solution using pOH
1. find pH value using -log(value)

2. Subtract that value from 14

3. answer

A larger Ka value for ionization of a weak acid indicates

more complete ionization

i.e Ka = 1.8e-5 > 5.8e-10, even tho both are weak acids

1. Calculate pH by doing 14 - pOH (8.84) and you get 5.16

2. Calculate the OH- ions by doing (OH-) = 10^-pOH

3. Calculate [H+] ions by doing [H+] = 10^-pH

1. Look at the acid, if it’s strong or weak. Strong means a full disassociation so it’ll match

2. Assign the directly known value

3. Use Kw = 1e-14 to get other ion

4. Calculate pH/pOH

When a problem says “placed in” that means those are the……!!!

initial values

You’re calcing Qc here and comparing to value of 15 to see which direction it will move

You solve this without using B because B’s a solid.

For ICE tables, what does X represent? (example of A and B reactants

The amount of A, B, required to get the initial amount of A and B to its equalibrium concentration following reactions stochiometry

If K is very small, and you end up with an equation where you CANNOT use quadratics to solve like

K = [B]³/(A) (can’t solve this because you end up with x³ + bx + c)

What do you do using the example problem shown?

1. Set up Ice table

2. Write the K expression

3. IF THE K IS VERY SMALL VALUE, REMOVE THE X ONLY FROM THE DENOMINATOR

4. Now you will be able to easily solve for X, and then can plug it back into the ICE table to solve.

If given A + 2B —> 3C
and 3C has an initial value of 0.5M

When you make the ICE table, do you cube the 0.5M before putting it into the initial value?

NO, only when solving for Kc.

For the following

4 + 4^×2 + -18x = (0.711 + 2x)²

How do you isolate for 0 to get the quadratic equation on right side?

1. remember a² + 2ab + b²

do 0.711²

then do 2 × 0.711 × 2x

then do b² which is 2x² —> 4x² (for this you’re basically just squaring the whole number while leaving the exponet on X, i.e (5x)² —> 25x²

Temp + = Endothermic

For percent ionization / percent error problems it will be

H+/initial HA concenentration

x 100

PLEASE ALWAYS WRITE THEM OUT THIS WAY IT WILL SIMPLIFY THINGS

You can do this man, you just need to remember which are strong acids and which are strong bases, then do addition of both to determine if its acidic, basic, or neutral

1. Split the component into 2 based on the element at the end

i.e Znbr —> Zn+ Br-

The CATion will come from the base, while the ANION will come from an acid, this is why you need to remember the strong acids and strong bases so you know which element is similar to one of those strong acids and bases!

2. Zn is a cation, weak base, the reason it’s weak is because Zn isn’t found in any of the strong bases, Br comes from a strong acid

• Add the effects (you’ll have to memorize these below)

Strong base (Ba, Sr, Ca, Cs, etc) : Neutral doesn’t affect pH

Weak base (NH4, C6H5NH3+) Acidic, lowers pH

Small metals: Zn, Al: Slightly acidic

Strong acid: Cl, Br, I : Neutral

Weak acid: F-, CH3COO, CN, HNO2, H2CO3: Basic : raises pH

Combine the effects of Zn (slightly acidic and Br-) neutral means the overall reaction is acidic

So the shortcut:

• Strong acid → [H₃O⁺] = initial

• Strong base → [OH⁻] = initial

• Only use Kw if you need the other ion.

This is an equation where you need kw, you know this because you’re given a Strong base (or if given a strong acid same idea), the (M) for the strong base will be the same for its relevant group (OH) , and you need to use kw to solve for the H3O group, it’s opposite ion

Remember this table

Strong base component (i.e Na+) + strong acid component (i.e Cl-)disassociating forms

a basic solution

1. ID the cation and Anion

2. ID if any component is a part of a strong acid or base

• if you have a component thats a strong acid or base, regardless cation or anion, its neutral

• If you have a component thats a weak base, i.e NH4, it’s acidic

• If you have a component thats a weak acid, i.e PO4, its basic

example

For pH predictions like the following problem, what do we do, and what should we ignore?

1. It’s just like before, write out and disassociate the element.

2. If it’s a component of a strong acid or base, it will be Neutral.

3. JUST REMEMBER THESE

• if it’s Fe³⁺, Al³⁺, Cr³⁺, Co³⁺

• Cu²⁺, Zn²⁺, Ni²⁺, Pb²⁺, Sn²⁺

• Be²⁺, Cr³⁺, Fe³⁺, Al³⁺

These will raise the pH and make it more basic

ignore water

Ranking questions

1. Calculate Kb for all of them

2. List the Kb’s

3. Rank the Kb’s from strongest to weakest (the one closest to 0 is the strongest with the lowest exponet i.e 1e^-2 > 1e^-4

ka x kb = kw

where ka is given

and kw = 1.00e-14

1. Write out disassociatoion

2. Look at the strength of the cation and anion

Cation (CH3NH3) - from a weak base = acidic

Anion (Br) - from a strong acid (neutral)

2. Solve for Ka using Kb + Kw

3. do Ka = Products/reactants (not including water)

4. Make an Ice table for the disassociation to get X

5. Solve for X using Ka

6. Remember you can simplify if Ka is very small

7. Once you solve for X, plug it into equation for H₃O conc in ice table

8. You can use the H₃O conc to find pH by doing the negative log one

****IMPORTANT

• ANY COMPONENT OF A STRONG ACID OR BASE HAS NO EFFECT ON PH, SO WHEN YOU DO STEP 1 AND WRITE IT OUT, DON’T INCLUDE THE STRONG ACID OR BASE

• i.e NaClO

• Na + Cl is neutral

• However NaClO is Na + ClO where Na doesn’t have an effect on pH

Therefore you write

ClO- + H2O ←→ HClO- + OH

ALSO VERY IMPORTANT

• THE REASON you bother to identify them as cations and anions (cations = base) (anions = acids) is because it helps you to know whether to use Ka or Kb to solve.

• For example in NaC2H3O2, Na is a strong base +, and neutral so disregard

• C2H3O2 must be an anion acid, however its not a strong acid. its a weak acid, therefore it will increase pH and it will form an OH on the other side. This tells you YOU MUST USE KB, BECAUSE THE ONE YOU’RE SOLVING FOR IS KB.

this is important because if you set up the written out equation wrong, you’ll end up using wrong k value and your shit will be wrong.

Thats why sometimes you have to solve for Kb when given Ka, because the thing you’re trying to solve for (C2H3O2) is increasing pH, so its a weak acid acting as a base.

so in summary

1. ID the cation (base) and the anion(acid)

2. ID the strength of base and acid

3. if the acids weak, then you’re gonna use kb to solve because pH will increase. If the base is weak you’re gonna use ka to solve because the pH will decrease

4. set up ice table

5. solve for X

6. solve for pH

For acids with same central atom, the more oxygens attatched, the stronger it is

1. Rewrite each acid to id the alpha carbon

• HC₂F₃O₂ → CF₃COOH

• HC₂Cl₃O₂ → CCl₃COOH

• HC₂BrH₂O₂ → BrCH₂COOH

• HC₂H₃O₂ → CH₃COOH

2. Alpha carbon is always written in the middle, attatched to its RIGHT is a COOH group, and attatched to either its left, or its right is extra

3. Look at the extras, count the ones that are NOT hydrogens

4. F > Cl > Br > H

How many ionizable hydrogen atoms does each of the following acids have?

just count hydrogens that are bound to oxygens

for 1, there’s 3 oxygen bound to hydrogens

etc.

You might have to write them out

What’s a Lewis base?

What’s a Lewis acid?

Lewis Base = Electron pair doner

Lewis acid = Electron pair acid

How to tell if a Lewis Acid, Lewis Base, or Neither?

1. if lone pairs = lewis base

2. if no lone pairs, but + = lewis acid

3. If neutral and no lone pairs = neither

An acid and a base that differ by only one proton are called

conjugate

As the concentration of a weak base in water increases, what happens to percent ionization?

Decreases

How to ID conjugate acid-base and conjugate base-acid

Conjugate acids and base pairs only differ by 1 hydrogen!