Chemistry Flashcards
(20 cards)
What is the formula to calculate pH from [H+]?
pH = -log[H+]
How do you calculate [OH-] if the pH = 5.4?
Use pOH = 14 - pH = 8.6, then [OH-] = 10^-pOH = 2.51 × 10^-9 M.
What is the freezing point depression equation?
ΔTf = Kf × m (where m is molality)
How do you calculate molality (m)?
m = moles of solute / kilograms of solvent
What is the difference between molarity and molality?
Molarity is moles per liter of solution; molality is moles per kilogram of solvent.
What does Hess’s Law state?
The total enthalpy change of a reaction equals the sum of enthalpy changes of steps leading to it.
How do you calculate heat absorbed or released?
q = m × C × ΔT
What is the combined gas law formula?
(P1 × V1) / T1 = (P2 × V2) / T2
What does the ideal gas law equation look like?
PV = nRT
What is a net ionic equation?
An equation showing only the ions and molecules directly involved in a chemical reaction, omitting spectator ions.
What are spectator ions?
Ions that do not participate in the actual chemical change and appear unchanged on both sides of the equation.
How do you identify the limiting reagent?
Calculate moles of each reactant; the reactant that produces the least product limits the reaction.
What are the three rules to write electron configurations?
Aufbau principle, Pauli exclusion principle, Hund’s rule.
What effect does increasing pressure have on a reaction with fewer gas moles on the product side?
It shifts the equilibrium toward the side with fewer gas molecules (usually products).
How do you calculate pH of a weak acid given Ka and initial concentration?
Set up Ka = [H+]² / ([HA]₀ - [H+]) and solve for [H+], then pH = -log[H+].
What is the relationship between pH and pOH?
pH + pOH = 14 at 25°C.
How do you write the equilibrium constant expression for: Ag⁺ + CrO₄²⁻ ⇌ Ag₂CrO₄(s)?
Ksp = [Ag⁺]² [CrO₄²⁻] (solid is excluded)
What is the specific heat formula?
q = m × C × ΔT
How do you balance a combustion reaction for methanol CH₃OH?
Balance C, then H, then O atoms last.
What is the role of a catalyst in equilibrium reactions?
It speeds up both forward and reverse reactions but does not change equilibrium concentrations.
