disappearance of NO in ...- Help!!!?
The following data were collected for the rate of disappearance of NO in the reaction 2 NO(g) + O2(g) �¨ 2 NO2(g).
Run: [NO](M) [O2](M) Initail Rate (M/s)
1 .0126 .0125 1.41 X 10^-2
2 .0252 .0125 5.64 X 10^-2
3 .0252 .0250 1.13 X 10^-1
(a) What is the rate law for the reaction?
(b) What are the units of the rate constant?
(c) What is the average value of the rate constant calculated from the three data sets?
(d) What is the rate of disappearance of NO when [NO] = 0.0750 M and [O2] = 0.0100 M?
(e) What is the rate of disappearance of O2 at the concentrations given in part (d)?
please explain!
a) NO doubles = rate quadruples
NO is 2nd rate (2^2 = 4)
O2 doubles = rate doubles
O2 is 1st rate (2^1 = 2)
b) M^-2s^-1
c) 1 = 7105 M-2s-1
2 = 7105 M-2s-1
3 = 7118 M-2s-1
avg = 7109 = 7110 M-2s-1
d) rate = 7110(0.0750)^2(0.0100)
rate = 0.400 M/s
e) 1/2 rate of disappearance of NO
0.400 / 2 = 0.200 M/s
To determine the rate law for the given reaction, we can examine the initial rates of each run and how they change with respect to the initial concentrations of NO and O2.
(a) To find the rate law, we need to compare the initial rates from each run and see how they are influenced by the concentrations. Looking at run 1 and run 2, we can see that when [NO] is doubled while [O2] remains constant, the rate quadruples. This suggests that the rate depends on the square of the concentration of NO. Therefore, the rate law for the reaction is Rate = k[NO]^2.
(b) The rate constant, k, represents the proportionality constant relating the rate of the reaction to the concentrations of the reactants raised to their respective powers in the rate law. Therefore, the units of the rate constant can be calculated by substituting the units of concentration and the rate into the rate law equation.
In the given data, the concentration of NO is given in moles per liter (M) and the rate is given in moles per second (M/s). Since the rate constant is determined by dividing the rate by the concentration(s) raised to their powers, the units of the rate constant are (M/s) / [NO]^2.
(c) To calculate the average value of the rate constant, we can use the data provided. Take the rate equation from run 1:
Rate = k[NO]^2
Plugging in the given values:
1.41 X 10^-2 (M/s) = k(.0126 M)^2
Solving for k, we get:
k = (1.41 X 10^-2 M/s) / (.0126 M)^2
By following a similar procedure for runs 2 and 3, you can find k for each run. Then, calculate the average of the three values to get the average value of the rate constant.
(d) To find the rate of disappearance of NO when [NO] = 0.0750 M and [O2] = 0.0100 M, we can use the rate law equation:
Rate = k[NO]^2
Substituting the given concentrations:
Rate = k(0.0750 M)^2
Calculate the value using the average rate constant found in part (c).
(e) To find the rate of disappearance of O2 at the concentrations given in part (d), we need to consider the stoichiometry of the reaction. From the balanced equation, we see that two moles of NO are consumed for every mole of O2. Therefore, the rate of disappearance of O2 will be half the rate at which NO is consumed.
Look at trial 1 versus 2. O2 is same concn; NO is doubled. What happens to the rate? It is 4x (0.0141 x 4 = 0.0564 so the reaction is second order with respect to NO.
Now compare trial 2 versus trial 3. (NO) is constant while O2 changes by a factor of 2 (0.125 to 0.250). How much did the rate change? Looks like it doubled (0.0564 x 2 = 0.1128 or 0.113)? So double O2 and we double rate which makes O2 first order.
rate = k(NO)2(O2)1 and you really don't need the 1.
The site I left last time will answer b for you.
For c, use the rate law you have from part a and substitute the data in the three trials. Solve for k and take the average.
i don't know how to do any of it
Instead of me doing all of the typing why don't you show what you know how to do and explain clearly what you don't understand about the other parts. I can help you through the tough spots.
By the way, you can go to this site and read units for orders 1,2,and 3.
http://en.wikipedia.org/wiki/Reaction_rate_constant