Rates
If the rate of appearance of O2 in the reaction:
2O3(g)--> 3O2(g)
is 0.250 M/s. Over the first 5.50 s, how much oxygen will form during this time?
1.38M
What percentage of a material will persist after 80 minutes if it’s half life is 20 minutes?
a. 50% b. 33% c. 25% d. 12.5% e. 6.25%
e. 6.25
What is the total reaction order?
rate= k[NO2]2[O2]
third
Which of the following combinations would give a pH of 7.00 at the "equivalence point" (when equal moles of each have been added)?
a) HCl + KF
b) HCN + NaOH
c) HF + HCl
d) HCl + KOH
d) HCl + KOH
Write an expression for the equilibrium constant for this reaction.
N2O4(g) + O3(g) <> N2O5(s) + O2(g)
. K=[O2]/[N2O4][O3]
A scientist conducts an experiment to determine the rate of the following reaction: N2(g) + O2(g) → 2NO(g)
If the initial concentration of N2 was 0.500 M and the concentration of N2 was 0.450 M after 0.100 s, what is the rate of the reaction?
0.5 M/s
show problem 23
first order
What is the total reaction order?
rate= k[O3][Cl]
second
When the following chemicals are mixed, each in 1 liter of water, which would give a basic pH at the end?
a)1mole of KOH and 1mole of HF
b) 1.0 mole of KOH and 1.0 mole of HCl
c)1 mole of HCl and 1 mole of NH3
d) 0.5 mole of KOH and 1.0 mole of HCl
a)1mole of KOH and 1mole of HF
Which of the following occurs when reactants are added to a chemical reaction in solution or the gas phase at equilibrium?
a. Q increases, so the equilibrium shifts to produce more products.
b. Q increases, so the equilibrium shifts to produce more reactants.
c. Q decreases, so the equilibrium shifts to produce more products.
d. Q decreases, so the equilibrium shifts to produce more reactants.
e. Q is unchanged by the addition of reactants.
Q decreases, so the equilibrium shifts to produce more products.
Collision theory assumes that the rate of a reaction depends on __________
a. the energy of collisions.
b. the orientation of colliding molecules.
c. the energy of collisions and the orientation of colliding molecules.
d. the change in energy between the products and the reactants. e. the change in free energy between the reactants and products
c. the energy of collisions and the orientation of colliding molecules.
show problem 24
C) first
Step 1: Cl(g) + O3(g) → ClO(g) + O2(g)
Step 2: ClO(g) + O3(g) → Cl(g) + 2O2(g)
What is the intermediate?
ClO
Identify all the correct statements about an acid–base buffer solution.
I. It can be prepared by combining a strong acid with a salt of its conjugate base.
II. It can be prepared by combining a weak acid with a salt of its conjugate base.
III. It can be prepared by combining a weak base with its conjugate acid.
IV. The pH of a buffer solution does not change when the solution is diluted V. A buffer solution resists changes in its pH when an acid or base is added to it.
a. I,II,IV b. II, III, V c. II, III, IV. d. I️, II, IV, V. e. II, III, IV
C
Which of the following are equal for a chemical system at equilibrium? If all are equal, answer E.
a. the concentrations of reactant and products are equal
b. the rate constants for the forward and reverse reactions are equal
c. the time that a particular atom or molecule spends as a reactant and product are equal
d. the rate of the forward and reverse reaction
e. all of the above are equal
d. the rate of the forward and reverse reaction
Which of the following statements is false:
Changing the temperature does not change the activation energy for a reaction
At higher temperature a higher percentage of reactants have enough energy to get over the transition
state
The mechanism, rate law, and activation energy will all change when a catalyst is added.
The general rate law for a reaction does not changes with temperature, but the rate constant does change
The rate constant “k” for a reaction does not change when the temperature increases.
5. The rate constant “k” for a reaction does not change when the temperature increases.
The first-order reaction A → B, has k = 8.00 s–1. If [A]0 = 0.500 M, how long will it take [A] = 0.200 M? (think integrated rate law)
0.115s
Step 1: NO2(g) + NO2(g) → NO3(g) + NO(g)
Step 2: NO3(g) + CO(g) → NO2(g) + CO2(g) Which of the following species is an intermediate?
NO3
Calculate the pH of a solution that’s 0.65M in NaF and 0.75M in HF. (HF, Ka = 7.2 × 10–4)
43. Find final equilibrium concentrations for HA, H+ , and A- :
HA. <> [H+] + A- Kc = 5.0 x 10-9
Initial Concentrations 0.30 0 0
43. [H+ ]=[A- ]=3.9 x 10-5 , [HA]=0.30
For the reaction 1A + 2B + 1C -> 2D + 1E, the rate law is: rate =k [B]2[C]1 Which of the following statements is false:
the reaction is first order in [A]
the reaction is second order in [B]
the reaction is first order in [C]
the reaction is third order overall
show problem 29
C. Rate = k[NO]^2 [Cl2]
Step 1: H2(g) + 2NO(g) → N2O(g) + H2O(g) (SLOW)
Step 2: N2O(g) + H2(g) → N2(g) + H2O(g) (FAST)
What is the rate law?
Rate = k[H2][NO]2
Calculate the pOH of a solution that’s 0.65M in NaNO2 and 0.40M in HNO2. (NaNO2, Ka = 4.0 × 10–4)
What is the equilibrium concentration of Br2 if [HBr] = 0.35 M and [H2] = 0.22 M at equilibrium?
H2(g) + Br2(g) 2HBr(g) K = 62.5
concentration = 8.9 x 10^-3