NO reacts with Br2 in the gas phase according to the following chemical equation: 2NO(g) +Br2(g)2NOBr(g) It is observed that, wh
1 answer:
Answer:
a)
b)
Explanation:
First of all you need to indicate the reaction order of each reactant ( and
):
1.
Note that if concentration (
) is reduced to 1/3 of its initial value, the rate of the reaction is also reduced to 1/3 of its initial value, it means:
then
As the change in the rate of the reaction is equal to the change of the initial concentration of , you could concluded that the reaction is first order with respect to
2.
Now, note that if concentration (
) is multiplied by 3.69, the rate of the reaction increases by a factor of 13.6. In this case, to know the ratio could be advisable divide the rate of the reaction (13.6) over the factor whereby was multiplied the concentration (3.69), as follows:
As the result is the same factor 3.69 you could concluded that the change of the rate of reaction is proportional to the square of the concentration of A:
It means that the reaction is second order with respect to
3. Rate Expression
Remember that the rate expression of the reactions depend on the concentration of each reactant and its order. In this case we have 2 reactants: and
, then we have a rate law depending of 2 concentrations, as follows:
Note that the expression is the result of the concentration of each reactant raised to its reaction order (previously determined)
<em>Note: I hope that you do not mix up the use of the rates of reaction of each reactant, that is experimentally determined, with the stoichiometric coefficient, are different.</em>
4. Rate constant units (k)
Assuming concentration is expressed as and time is in second, to find the units of k we need to solve an equation with units and with supporting of the rate equation previously obtained, as follows:
Where:
Then:
The units of the rate constant k are:
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Answer:
Explanation:
Previous concepts
Angular momentum. If we consider a particle of mass m, with velocity v, moving under the influence of a force F. The angular momentum about point O is defined as the “moment” of the particle’s linear momentum, L, about O. And the correct formula is:
Applying Newton’s second law to the right hand side of the above equation, we have that r ×ma = r ×F =
MO, where MO is the moment of the force F about point O. The equation expressing the rate of change of angular momentum is this one:
MO = H˙ O
Principle of Angular Impulse and Momentum
The equation MO = H˙ O gives us the instantaneous relation between the moment and the time rate of change of angular momentum. Imagine now that the force considered acts on a particle between time t1 and time t2. The equation MO = H˙ O can then be integrated in time to obtain this:
Solution to the problem
For this case we can use the principle of angular impulse and momentum that states "The mass moment of inertia of a gear about its mass center is ".
If we analyze the staritning point we see that the initial velocity can be founded like this:
And if we look the figure attached we can use the point A as a reference to calculate the angular impulse and momentum equation, like this:
And if we integrate the left part and we simplify the right part we have
And if we solve for we got:
