Flask is charged with 0.100 mol of A and allowed to react to form B according to
ID: 1004417 • Letter: F
Question
Flask is charged with 0.100 mol of A and allowed to react to form B according to the hypothetical gas-phase reaction A(g) rightarrow B(g). The following data are collected: Calculate the number of moles of B at each time in the table, assuming that A is cleanly converted to B with no intermediates, Calculate the average rate of disappearance of A for each 40-s interval in units of mot's. Which of the following would be needed to calculate the rate in units of concentration per time: (i) the pressure of the gas at each time. (ii) the volume of the reaction flask, (iii) the temperature, or (iv) the molecular weight of A? Consider the following reaction: 2 NO(g) + 2 h2(g).N2(g) + 2 H2O(g) The rate law for this reaction is first order in H2 and second order in NO. Write the rate law. If the rate constant for this reaction at 1000 K is 6.0 * 10^4 M^-2 s^-1. what is the reaction rate when [NO] = 0.035 M and [H2] = 0.015 What is the reaction rate at 1000 K when the concentration of NO is increased to 0.10 M, while the concentration of 112 is 0.010 What is the reaction rate at 1000 K if [NO] is decreased to 0.010 .1/and [H2] is increased to 0.030 M? For each of the following gas-phase reactions, write the rate expression in terms of the appearance of each product and each reactant:Explanation / Answer
Solution:- (1) The given equation is.....
A(g) --------------> B(g)
(a) There is 1:1 mole ratio between A and B, So, the moles of B formed would be equal to the moles of A used.
Initially we only have taken moles of A so moles of B at zero time would also be 0. The sum of moles of A abd B must be 0.100 at any time. So, we could fill the table as..
time (s) moles of A moles of B
0 0.100 0
40 0.067 0.033
80 0.045 0.055
120 0.030 0.070
160 0.020 0.080
(b) average rate is change in moles divide change in time.
so, average rate = change in moles of A/change in time
let's make the table for this...
time (s) moles of A Average rate of disappearance of A (mol/s) per 40 sec interval
0 0.100
40 0.067 (0.067 - 0.100)mol/40s = -0.000825 mol/s
80 0.045 (0.045 - 0.067)mol/40s = -0.00055 mol/s
120 0.030 (0.030 - 0.045)mol/40s = -0.000375 mol/s
160 0.020 (0.020 - 0.030) mol/40s = -0.00025 mol/s
(c) to calculate the rate in units of concentration per time that is molarity per time we need the volume of the reaction flask since we are given with moles and to convert these moles into molarity, we need the volume as molarity is mol/L.
So, the correct choice is (II) the volume of the reaction flask.
(2) The given reaction is.....
2NO(g) + 2H2(g) -----------> N2(g) + 2H2O(g)
(a) In general the rate law is written as........
rate = k [A]n [B]m
where k is the the rate constant, [A] is concentration of A and n is its order of reaction. Likewise, [B] is the concentration of B and m is its order of reaction.
For the given reaction, the reactants are NO and H2 and the order with respect to rach of these are given. so, the rate would be...
rate = k [H2] [NO]2
(b) let's plug in the values in the rate law...
rate = 6.0 x 104 M-2 s-1 x [0.015M] [0.035M]2
rate = 1.1 M s-1
(c) Since the temperature is same, rate constant would also remain the same. Hence..
rate = 6.0 x 104 M-2 s-1 x [0.010M] [0.10M]2
rate = 6.0 M s-1
(d) rate = 6.0 x 104 M-2 s-1 x [0.030M] [0.010M]2
rate = 1.8 x 10-1 M s-1
(3) Let's take a hypothetical equation... aA + bB ------< cC + dD
rate = (-1/a)delta[A]/delta t = (-1/b) delta[B]/delta t = (1/c) delta[C]/ delta t = (1/d) delta[D]/ delta t
so, what we notice from this is.... The coefficients are inverted and there are negative signs for the reactants which indicates a decrease in their concentration as the time increases. delta [] is change in concentrations and delta t is change in time since rate is change in concentration per unit of time.
Now, we could write this for the reaction reactions..
(a) rate = (-1/2)delta[H2O]/delta t = (1/2) delta[H2]/delta t = delta[O2]/ delta t
(b) rate = (-1/2) delta[SO2]/ delta t = -delta[O2]/delta t = (1/2) delta[SO3]/delta t
(c) rate = (-1/2) delta[NO]/delta t = (-1/2) delta[H2]/delta t = delta[N2]/delta t = (1/2) delta[H2O]/delta t
(d) rate = -delta[N2]/delta t = (-1/2)delta[H2]/delta t = delta[N2H4]/delta t
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.