Flashcards
Chapter 15: Chemical Equilibrium
Cards in this deck (70)
- 1a reaction with a _____ equilibrium constant proceeds nearly to completionlarge
- 2K or Kᶜ ᶜ = concentration-equilibrium constant
- depicts [] of reactants/products in a reaction at equilibrium
- measure of how far a reaction proceeds
- gases and aqueous states only
- changes only w/change in temperature - 3what does a large value of K mean- K >> 1
- reaction lies far to the right at equilibrium
- a high [] of products and a low [] of reactants
- reaction goes to completion then reverses back to reach equilibrium - 4what does a low value of K mean- K << 1
- reaction lies far to the left at equilibrium
- reactant [] high & product [] low - 5dynamic equilibrium- forward reaction rate = reverse reaction rate
- dynamic cuz forward/reverse reactions are still occurring @ same rate
- reactant [] ≠ product []
- [] become constant - 6equilibrium constant (K) for a reaction formula- coefficients = exponents in * constant
- numerators: amt of products in *
- denominator: amt of reactants in *
* equilibrium - 7if a chemical equation is modified, the K for the equation _____.changes
- 8if we reverse the equationinvert K
- 9if we multiply the coefficients in the equation by a factorraise K to the same factor
- 10if we divide the coefficients in the equationtake the square root
N₂ + 3H₂ ⇄ 2NH₃ K = 5.6 × 10⁵
NH₃ ⇄ ½N₂ + H₂ ⅔H₂ K = ?
K = √(1/5.6 × 10⁵) or (1/5.6 × 10⁵)¹/² - 11if we add 2 or more individual equationsmultiply corresponding Ks by each other
- 12chemical equation A ⇄ 2B w/ K=0.010 changes to B ⇄ ½A. what is the equilibrium?- eq reversed → invert K
- eq divided by 2 → square root K
K = 10 - 13give K for Cu(s) + 2Ag(aq) ⇄ Cu(aq) + 2Ag(s)[Cu²⁺] / [Ag⁺]²
- 14give K for CaCO₃(s) ⇄ CaO(s) + 2CO₂[CO₂]²
- 15give K for 2H₂O(l) ⇄ 2H₂ + O₂[H₂]²[O₂]
- 16find K CO₂ + 3H₂ ⇄ CH₃OH + H₂O K = ? CO + H₂O ⇄ CO₂ + H₂ K₂ = 1.0 × 10⁵ CO + 2H₂ ⇄ CH₃OH K₃ = 1.4 × 10⁷write equation 2 in reverse order
CO₂ + H₂ ⇄ CO + H₂O K₂ = 1/(1.0 × 10⁵)
add equation 2 & 3 to get equation 1
CO₂ + H₂ ⇄ CO + H₂O
CO + 2H₂ ⇄ CH₃OH
K = K₂ × K₃ = 1.4 × 10² - 17for gaseous reactants, partial pressure is proportional to its _____concentration
- 18can express K in terms of _____ _____partial pressures
- 19Kᶜequilibrium constant w/respect to [] in M
- 20Kₚ- for gases only
- same expression as Kᶜ
- use the partial pressure of each gas instead of [] - 21Kₚ formula
- 22partial of a gas in atm _____ as its concentration in molarityisn't
- 23Kₚ for a reaction ____ _____ = to Kᶜisn't
necessarily - 24deriving relationship between Kₚ and Kᶜ
- 25Kₚ formula 2Δn: (sum product coef) - (sum reactant coef)
if Δn = 0 → Kₚ = Kᶜ
- 26[] of _____ and _____ _____ does not change. So they are _____ from the equilibrium expression. their constant value are _____ into the value of _____.solids
pure liquids
excluded
incorporated
K - 27Because equilibrium constants depend on _____, many equilibrium problems state the _____ even though it has no part in the calculationtemp
temp - 28ICE example: part 1 2CH₄ (g) ⇄ C₂H₂ (g) + 3H₂ (g) init [CH₄] = 0.087 M. @ equilibrium [H₂] = 0.012 M. Find equilibrium constant.
![ICE example: part 1 2CH₄ (g) ⇄ C₂H₂ (g) + 3H₂ (g) init [CH₄] = 0.087 M. @ equilibrium [H₂] = 0.012 M. Find equilibrium constant.](https://examtimeassets.s3.amazonaws.com/uploads/media/image/21446381/desktop_e4855a4e-9807-4616-b45f-94354dcc087f.png)
- 29—
- 30reaction quotient- gauges reaction progress toward equilibrium
- @ equilibrium K = Qᶜ
- same formula as K, use Qᶜ or Qᵖ instead
- reaction doesn't have to be at equilibrium - 31Qᶜ = 0mixture contains only reactants
- 32Qᶜ = ∞mixture contains only products
- 33Q < K- reaction goes to right, toward products
- Q gets larger as reaction → equilibrium and [reactant] ↓ and [product] ↑ - 34Q > K- reaction goes to left, toward reactants
- gets smaller as reaction → equilibrium and [reactant] ↑ and [product] ↓ - 35Q = K- reaction is at equilibrium
- 36Predicting direction of reaction I₂ + Cl₂ ⇄ 2ICl Kₚ = 81.9 PI₂ = 0114 atm, PCl₂ = 0.102 atm, PICl = 0.355atm
- 37small K method- K <= 10⁴
- drop "- X" or "+ x" from the eq & solve
- reaction has more reactants > products
- reverse reaction favored over forward reaction
- x (change in []) very small - 38small K example
- 39for A(g) ⇄ B(g), which [] will small approximation most likely apply to K = 1.0 × 10⁻⁵ [A] = 0.250 M K = 1.0 × 10⁻⁵ [A] = 0.00250 MK = 1.0 × 10⁻⁵ [A] = 0.250 M
- 40small approximation is most likely to apply to a reaction w/small K & an [A]₀ that is not too _____. The bigger the K and smaller the [A]₀ the _____ likely the small approximation will applysmall
smaller
less - 41Large K method- K > 10⁴
- reaction has products > reactants
- forward reaction favored over reverse reaction
- x (change in []) very large - 42Large K method stepsStep 1: Find limiting reactant
Step 2: Get x
Step 3: Find [] of product
Step 4: Find left over [] of reactant that wasn't limiting agent
Step 5: Reverse equation
Step 6: Use ICE, get equilibrium [] - 43Large K method example: step 1 1.85M gas A is mixed w/0.432M of gas B Chemical equation: 2A(g) + B(g) ↔ 2 C(g). K = 6.50 ×10⁶ at 25 °C Calculate the equilibrium [] of B?step 1: Find limiting reactant
2A(g) + B(g) ↔ 2 C(g). Assume volume = 1L to get M
- 44Large K method example: step 2, 3 and 4
- 45Large K method example: step 5 and 6
- 46Le Chatelier's principle- states when a chemical system at equilibrium is disturbed, the system shifts in a direction that minimizes the disturbance
- K values stay the same - 47Le Chatelier's principle Addition of reactantN₂(g) + 3H₂(g) ↔ 2NH₃(g)
- shifts to right (forward), towards product
- More NH₃ will be formed
- Q < K - 48Le Chatelier's principle Addition of productN₂(g) + 3H₂(g) ↔ 2NH₃(g)
- shifts to left (reverse), towards reactant
- More N₂ and H₂ will be formed
- Q > K - 49Le Chatelier's principle Removal of reactantN₂(g) + 3H₂(g) ↔ 2NH₃(g)
- shift toward reactant
- More N₂ and H₂ will be formed
- Q > K - 50Le Chatelier's principle Removal of productN₂(g) + 3H₂(g) ↔ 2NH₃(g)
- shift toward product
- More NH₃ will be formed
- Q < K - 51changing the volume of a gas/gas mixture results in a change inpressure
- 52pressure and volume are _____ relatedinversely
- 53a ______ in volume causes an increase in pressure, an an _____ in volume causes a decrease in pressuredecrease
increase - 54ideal gas law formulaPV = nRT
- 55decreasing the number of _____ of a gas (n) results in a _____ pressure (P)moles
lower - 56Le Chatelier's principle increase in pressureN₂(g) + 3H₂(g) ↔ 2NH₃(g)
- shifts to lesser mole side, right (forward), towards product
- More NH₃ will be formed
- Q < K - 57Le Chatelier's principle decrease in pressureN₂(g) + 3H₂(g) ↔ 2NH₃(g)
- shifts to larger mole side, left (reverse), towards reactant
- More N₂ and H₂ will be formed
- Q > K - 58Le Chatelier's principle increase in volumeN₂(g) + 3H₂(g) ↔ 2NH₃(g)
- shift to the larger mole side, left (reverse) towards reactant
– More N₂ and H₂ will be formed - 59Le Chatelier's principle decrease in volumeN₂(g) + 3H₂(g) ↔ 2NH₃(g)
- shift to the lesser mole side, right towards product
– More NH₃ will be formed - 60Le Chatelier's principle pressure/volume detailSame moles on both sides, No effect due to Change in P, V
- 61when a reaction has an = # of moles of gas on both sides of the chemical equation, a change in volume produces _____ effects on equilibriumno
- 62changes in volume or concentration change _____ not _____, and the system responds by shifting so that _____ = _____Q
K
Q
K - 63change in temp _____ the value of the equilibrium constantchanges
- 64if we increase the temp of a reaction mixture at equilibrium, the reaction shifts in the direction that tends to _____ the temp and vice versadecrease
- 65Exothermic Reaction can be represented asA(g) + B(g) ↔ C(g) + Heat
ΔH < 0
- can think of heat as a product
- emits heat - 66Endothermic Reaction can be represented asA(g) + Heat ↔ B(g) + C(g)
ΔH > 0
- can think of heat as a reactant
- absorbs heat - 67Le Chatelier's principle raising temp in exothermic reaction- adding heat, similar to adding more product
- shift left, towards reactant
- value of K decreases
- new mixture will have more reactants & less products - 68Le Chatelier's principle lowering temp in exothermic reaction- shift right, towards product
- value of K increased
- releases heat and produces more products - 69Le Chatelier's principle raising temp in endothermic reaction- adding heat
- shift right to absorb the added heat
- value of K increases
- produces more products - 70Le Chatelier's principle lowering temp in endothermic reaction- removing heat
- shift left, releasing heat, forming fewer products
- value of K decreases
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- General Chemistry (Chem II) Flashcards on Chapter 15: Chemical Equilibrium, created by Alexandra Bozan on 19/07/2019.
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