In: Chemistry
1. Which relationship of reaction rates is correct for the following reaction?
2Na2CO3(aq) + 4NO(g) + O2(g) ---> 4NaNO2(aq) + 2CO2(g)
a. -Δ[NO]/Δtime= -Δ[O2]/Δtime
b. -Δ[NO]/Δtime= -Δ[NaNO2]/Δtime
c. Δ[NaNO2]/Δtime = (1/2)(Δ[CO2]/Δtime)
d. Δ[NaNO2]/Δ time= -(4)(Δ[O2]/Δtime)
e. Δ[O2]/Δtime = (2)(Δ[CO2]/Δtime)
4. Which statement is NOT true for the reaction
C + D ---> F + G if the rate law is
rate = k[C]2[D]1/2?
a. If the concentration of D is increased by a factor of 4, then the reaction rate will double.
b. If the concentration of C is doubled and the concentration of D is tripled, then the reaction rate will increase by a factor of 6.9.
c. If the concentration of C is increased by a factor of 3 and the concentration of D is
decreased by a factor of 4, then the reaction rate will increase by a factor of 4.5.
d. If the concentrations of C and D are doubled, then the reaction rate will triple.
e. If the concentration of C is increased by a factor of 4, then the reaction rate will
increase by a factor of 16.
5. Which statement is true regarding the experimental determination of a rate law?
a. In order to determine the value of an exponent for a reactant in the rate law, the concentration of that reactant and one other reactant must be changed.
b. The instantaneous rate at the midway point of the reaction is used to determine the exponents and rate law for that equation.
c. The average rate of reaction at the midway point of the reaction is used to determine the exponents and rate law for that equation.
d. The concentration of one reactant is varied and the remaining reactants are unchanged to determine the value of the exponents for the reactants in a rate law.
(1) The correct option is (d)
For the given reaction general rate can be written as follow
-1/2 [Na2CO3] / t = -1/4 [NO] / t = - [O2] / t = 1/4 [NaNO2] / t = 1/2 [CO2] / t
Or, we can also write - [O2] / t = 1/4 [NaNO2] / t
Above equation can also be written as - 4 [O2] / t = [NaNO2] / t
This is option (d)
(4) The state d is wrong
Given rate = k[C]2[D]1/2
Concentration of C and D is doubled
Rate = k[2C]2[2D]1/2
= (2)2 (2)1/2 [C]2[D]1/2
= 4 x 1.414 [C]2[D]1/2
= 5.6 [C]2[D]1/2
Reaction rate is not tripled as given in statement d therefore correct option is (d)
(5.) The correct option is d.
This is method of initial rate is descibed in option d which is used in lab to find the exponents for the reactants.