AP CHEM EXAM REVIEW

Heat released (q)=

=(n) (delta H/ enthalpy)

Explain why qair=-qrxn

heat lost or gained by the surroundings (in this case, air) is equal in magnitude but opposite in sign to the heat released or absorbed by the reaction (the system).

When a reaction is exothermic, heat is thought of as a

product

When a reaction is endothermic, heat is thought of as a

reactant

Equillibirum: To influence pressure, you…

change volume (decreasing volume would favor the side of the reaction with fewer mols, increasing volume would favor the side with more mols)

Catalyst doesn’t get consumed in reaction it just

speeds it up/ lowers the activation energy

In order to be zero order…

the rate of mass loss (rate of reaction) must be constant until the reactant was consumed

At the equivalence point,

mols acid=mols base

Kw=

[H+][OH-]

• A saturated solution is

• one in which no more solute can dissolve at a given temperature. (the solution already holds as much dissolved solute as possible at that temperature

Molarity is in units of

Liters

Increasing the surface area of the reactant

increases the rate of the reaction, because more of the solid is in contact with the ions in solution.

If OH- is formed

the solution is at least slightly basic

if H3O+/H+ is formed

the solution is at least slightly acidic

What happens to the acid at the equivalence point in a titration?

At the equivalence point, the moles of acid equal the moles of base added. The original acid has completely reacted and is no longer present.

• In a strong acid–strong base titration, only neutral salt and water remain (pH ≈ 7).

• In a weak acid–strong base titration, the acid is converted entirely into its conjugate base, which remains in solution and can make the solution basic (pH > 7).

• So, while moles acid = moles base added, the original acid = 0 mol left.

All sodium salts

are soluble/ dissolve in water

Ionic compound generally exists as —— at room temperature

solid

Q vs K

Q —→ K ←—- Q

when Keq is greater than 1 (favorable),

ΔG° must be negative. (for a favorable reaction)

How do you determine which substance has a higher equilibrium vapor pressure?

• Weaker forces (like London dispersion) → easier to evaporate → higher vapor pressure

• Stronger forces (like hydrogen bonding or dipole-dipole) → harder to evaporate → lower vapor pressure

Sulfur has an

expanded octet (can hold 8-12 v.e.)

Boron is the main element that only needs

6 valence electrons

Electron geometry describes———— while molecular geometry———- describes

electron: the arrangement of all electron groups (bonding and non-bonding) around a central atom Molecular: the arrangement of only the bonded atoms (more specific)

CHange in G should be given in units of

kJ

melting is..

endothermic and requires the flow of thermal energy into the material for phase change to occur.

A larger K value is

favorable

Beer’s law:

the amount of light absorbed by a substance is directly proportional to both the concentration of that substance and the distance the light travels through it. This means that the more of a substance there is, and the longer the path the light travels, the more light will be absorbed. 

Is the half-equivalence point always a buffer? Why or why not?

Yes — but only in weak acid–strong base (or weak base–strong acid) titrations.
At the half-equivalence point, half the weak acid (or base) has been neutralized, forming its conjugate base (or acid) → this creates a buffer system.

📌 At this point:

the concentration/mols of the acid= concentration/mols of the conjugate base

pH=pKa

⚠ Not a buffer in strong acid–strong base titrations — no weak species involved.

To flip the reaction of an equillibirum value you do…

1/K (for thermodynamic values like enthalpy you flip the sign)

What is the cause and effect of equilibrium?

• The cause of equilibrium is equal reaction rates.

• The effect is constant concentrations.