Chem. 2 Exam2

What does an acid do?

Give away H⁺

What does a base do?

Take H⁺

Arrhenius acids/bases

Acid makes H⁺ in water. Bases make OH- in water. Example: HCl gives H+. NaOH makes OH- in water.

Bronsted-Lowy acids/bases

Acids give H+. Bases take H+. Example: NH3 grabs H+ so its base becomes NH_4⁺

What does a base need to grab H+?

Extra electrons.

Does H+ have electrons?

H+ is “lonely” (no electrons). It wants electrons. Bases have electrons and they help. Bases have extra electrons (space to hold something).

Amphoteric

Can give H+ (acid) and take it (base). An example is water.

An example of Water being Amphoteric

HCl + H₂O → H₃O+. The water grabbed the H+

Conjugate pairs

They are the same thing, but missing/adding 1 H+

What is a trick for identifying conjugate pairs?

Look for difference of 1 H

Example of conjugate pairs

HCl gives H+ and it becomes Cl-. so, HCl, had a H, and its partner (Cl-) lost a H.

What is the difference between a strong vs. weak acid?

A strong acid give toys very easily (H), and weak acids dont want to give toys or doesn’t give much. Strong is generous, weak is stingy

A strong acid is a ____ base.

Weak

A weak acid is a ____ base.

strong

What is an example of a strong acid?

HCl. It gives all toys! (H)

What is an example of a weak acid?

CH₃COOH. It keeps most toys (H)

Which direction do reactions go?

The reaction goes towards weaker things. Strong —> Weak

What is an example of the way a reaction goes?

Strong acid + strong base → weak acid + weak base. Reaction goes → right

Water sometimes splits itself. How?

Water can break into H+ (toy) and OH- (extra toy holder). Remember: KW = 1.0 × 10^-14

What is the ion product of water?

KW = 1.0 × 10^-14

What is a good way to tell an acid from a base?

If the H+ is bigger, it is prob an acid. If the OH- is bigger, it is a base.

How do you calculate pH (question wise)

“How many toys (H+) are there?”

Low pH means there are lots of toys (H+). High pH means there are barely any toys.

Acid by definition is

pH > 7

Neutral pH by definition is

pH = 7

A base by definition is

pH > 7

pOH

“how many OH- (grabbers)”

Fromula for pOH

-log[OH-]

pH + pOH =

14

A tip to help if you get stuck solving for pOH

pH = 14 - pOH

Strong acids (like HCl) give away all their toys immediately with

No hesitation. And it happens 100% completely.

Weak acids (like HF) slowly hand out a few toys and they

only partially break. and they go back and forth (equilibrium)

Explain how to make an ICE table.

This is your equation: N2 + 3H2 -> 2NH3

(1) First you fill out the ice table, ICE on the side and your reactants stretched out across the top.

(2) The initials should be given to you. Say N2 = 1.0, H2 = 3.0, and NH3 = 0. Set that up in the table. Use the coefficients to determine how things change. N2 has 1, H2 has 3, and NH3 has 2. To decide the sign of those values, look at the equation and see what side it’s on. If it’s on the reactants side (left), negative. If on the products side (right) positive. Apply that.  Put that at C in the table. To get E, you will just do Initial (I) + Change (C). So for N2: 1.0-x. H2: 3.0-3x. NH3: 0 + 2x = 2x. And there you go, that is your table. Now, next part of this problem.

(3) Write the equilibrium in expression (Kc). Kc = [products^(coefficients)] / [reactants^(coefficients)]. So here you have Kc = [NH3]^2/[NH2]H2]^3. Plug in the equilibrium values and solve for x. (4) Once you get x, plug it back into the E row to get all concentrations.

At equilibrium —

Everything stops changing, but NOT everything is used up

When it regards to equilibrium x is

how much got used and how much got made

What is the formula for percent ionization? Out of all toys how many were given away

% = (H⁺ made / initial acid) × 100

Polyphonic acids

Have more than one H+ to give. They give away twice

Bases GRAB toys and make OH-. Here is an example problem:

NH₃ + H₂O ⇌ NH₄⁺ + OH⁻

How would you solve this?

Solve with ICE table, find OH- first, then convert pOH → pH

There is a balance rule that says

👉 If acid is strong → base is weak
👉 If base is strong → acid is weak

What formula shows this?

Ka * Kb = Kw

Salt can be acidic, basic, or neutral.

True

If salt makes H+ is becomes

acid

If salt makes Oh-, it is a

base

If salt makes nothing (No H+ or OH-), it is

neutral

Strong acid + strong base

neutral (problem)

Strong acid + weak base

Acidic

Weak acid + strong base

Basic

If the Ka is small

weak acid I

If the Ka is big

strong acid