Reaction Rate
What are the three factors that influence reaction rate?
* Concentration
* Physical State
* Temperature
What is the definition of half-life?
What factors are necessary for a reaction to happen?
Explain the difference between Q and K in a reaction
Q: the ratio of products over reactants at any point in the reaction
K: the ratio of products over reactants at equilibrium
K is expressed as (blank)/(blank)
(Products)/(Reactants)
Consider the following reaction:
A+4B → 3C
If [C] increases at the rate of 9.0 mol·L-1 s-1, at what rate is [B] changing?
-12.0 mol·L-1 s-1
Cyclopropane is the smallest cyclic hydrocarbon.
Because its 60 ̊ bond angles reduce orbital overlap, its bonds are
weak. As a result, it is thermally unstable and rearranges to propene
at 1000 ̊C via the following first-order reaction. The rate constant is
9.2 s-1.
What is the half-life of the reaction?
0.075 s
What is a Catalyst and how how does it affect a reaction?
A substance that increases the reaction rate by lowering the activation energy
If Q > K , which way will the reaction shift?
Shift left or towards the reactants.
What is the expression of K in the reaction;
HNO3(l) +ClF(g) —>ClNO2(g) + HF(g)
K= [ClNO2] [HF]/[ClF]
Write the general form reaction rate for the given reaction:
2CH4 + 4O2 → 2CO2 + 4H2O
Rate = -(1/2)(ΔCH4/ΔT) = -(1/4)(Δ4O2/ΔT) =
(1/2)(ΔCO2/ΔT) = (1/4)(ΔH2O/ΔT)
Which order has a positive slope in their integrated rate law form?
Second order
In the expression for the equilibrium constant Kc, these two physical states are omitted.
Solids and Liquids
Determine how much reactant and product you would have if a reaction had a small value of K
More reactant and less product.
Gaseous ammonia was heated in a sealed container to form nitrogen gas and hydrogen gas.
2NH3 (g) ⇌ N2 (g) + 3H2 (g)
At equilibrium, [NH3] = 0.0125 M, [N2] = 0.108 M and [H2] = 0.372 M. Calculate Kc for the reaction
K= 35.6
How do the units between a zero order and a second order constant differ?
* Zero Order: mol L–1 s–1
* Second Order: L mol–1 s–1
At 25 ̊C, hydrogen iodide breaks down very slowly to
hydrogen and iodine. The reaction is second order with respect to
hydrogen iodide. The rate constant at this temperature is 7.6 10 L / mol·yr
(a) If 0.0100 mol of HI(g) is placed in a 1.0-L container, how long will it take
for [HI] to reach 0.00900 mol/L?
1.46E14 years
A multi-step mechanism must have this rate-determining feature.
What is the slowest step?
Using Le Châtelier’s Principle, what happens to [O2] if H2S is removed in the following reaction
2H2S 𝑔 + O2 𝑔 ⇄ 2S 𝑠 + 2H2O 𝑔
When H2S is removed, Q increases and the reaction proceeds to the left until Qc = Kc, so [O2] increases.
At a particular temperature, Kc = 6.5 x 10^2 for the following reaction:
2NO (g) + 2H2 (g) ⇌ N2 (g) + 2H2O (g)
Calculate Kc for the following reaction:
NO (g) + H2 (g) ⇌ ½ N2 (g) + H2O (g)
K= 25 or 25.5
A reaction is first-order with respect to the reactant R. Which of the following plots will produce a straight line?
ln[R] vs. time
At 1000 ̊C, cyclobutane (C4H8) decomposes in a first-
order reaction, with the [very high] rate constant of 87 s−1, to two molecules of ethylene (C2H4).
The initial C4H8 concentration is 2.00 M. What is the
concentration after 0.010 s?
0.83 mol / L
Increasing the pressure on a gaseous equilibrium system will shift the reaction in this direction.
the direction with fewer moles of gas
How would you adjust the volume of the container in order to maximize the product yield in the following reaction?
Na2O2 (s) ⇌ 2 Na (l) + O2 (g)
Increase volume
2PH3 (g) ⇌ P2 (g) + 3H2 (g)
At 750 K, Kp = 19.6. In a reaction mixture at equilibrium, PPH3 = 0.112 atm and PP2 = 0.215 atm.
What is the equilibrium partial pressure of H2?
PH2 = 1.045 atm