Molar per second sounds a lot like meters per second, and that, if you remember your physics is our unit for velocity. So, average velocity is equal to the change in x over the change in time, and so thinking about average velocity helps you understand the definition for rate of reaction in chemistry.
If we look at this applied to a very, very simple reaction. So we have one reactant, A, turning into one product, B. Now, let's say at time is equal to 0 we're starting with an initial concentration of A of 1. So at time is equal to 0, the concentration of B is 0. Let's say we wait two seconds. So, we wait two seconds, and then we measure the concentration of A. Obviously the concentration of A is going to go down because A is turning into B. Let's say the concentration of A turns out to be. So we lost.
So that turns into, since A turns into B after two seconds, the concentration of B is. Right, because A turned into B. So this is our concentration of B after two seconds. If I want to know the average rate of reaction here, we could plug into our definition for rate of reaction.
Change in concentration, let's do a change in concentration of our product, over the change in time. So, the Rate is equal to the change in the concentration of our product, that's final concentration minus initial concentration. So the final concentration is 0. So, we write in here 0. So, 0. That's the final time minus the initial time, so that's 2 - 0.
So the rate of reaction, the average rate of reaction, would be equal to 0. So that's our average rate of reaction from time is equal to 0 to time is equal to 2 seconds. We could do the same thing for A, right, so we could, instead of defining our rate of reaction as the appearance of B, we could define our rate of reaction as the disappearance of A.
So the rate would be equal to, right, the change in the concentration of A, that's the final concentration of A, which is 0. Now this would give us So we need a negative sign. We need to put a negative sign in here because a negative sign gives us a positive value for the rate. So, now we get 0. So we get a positive value for the rate of reaction. All right, so we calculated the average rate of reaction using the disappearance of A and the formation of B, and we could make this a little bit more general.
We could say that our rate is equal to, this would be the change in the concentration of A over the change in time, but we need to make sure to put in our negative sign. We put in our negative sign to give us a positive value for the rate. So the rate is equal to the negative change in the concentration of A over the change of time, and that's equal to, right, the change in the concentration of B over the change in time, and we don't need a negative sign because we already saw in the calculation, right, we get a positive value for the rate. So, here's two different ways to express the rate of our reaction.
So here, I just wrote it in a little bit more general terms. Let's look at a more complicated reaction. Here, we have the balanced equation for the decomposition of dinitrogen pentoxide into nitrogen dioxide and oxygen.
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So what is the rate of formation of nitrogen dioxide? Well, if you look at the balanced equation, for every one mole of oxygen that forms four moles of nitrogen dioxide form. So we just need to multiply the rate of formation of oxygen by four, and so that gives us, that gives us 3.
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So, NO2 forms at four times the rate of O2. Solubility in water. Refractive index n D. Molecular shape. Dipole moment. Std molar entropy S o ATC code. Pregnancy category. US : C Risk not ruled out.
Routes of administration. Biological half-life. Related nitrogen oxides.
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