# The rate and order of a

Initial rate Reaction order Kinetics Video transcript - [Voiceover] Now that we understand how to write rate laws, let's apply this to a reaction. Here we have the reaction of nitric oxide, which is NO, and hydrogen to give us nitrogen and water at degrees C. A rate equation shows this effect mathematically. Orders of reaction are a part of the rate equation. This page introduces and explains the various terms you will need to know about. If you aren't sure about why changing concentration affects rates of reaction you might like to follow this link and come back to this page afterwards - either via the rates of reaction menu or by using the BACK button on your browser.

Rate equations Measuring a rate of reaction There are several simple ways of measuring a reaction rate. For example, if a gas was being given off during a reaction, you could take some measurements and work out the volume being given off per second at any particular time during the reaction.

A rate of 2 cm3 s-1 is obviously twice as fast as one of 1 cm3 s Read cm3 s-1 as "cubic centimetres per second". However, for this more formal and mathematical look at rates of reaction, the rate is usually measured by looking at how fast the concentration of one of the reactants is falling at any one time.

For example, suppose you had a reaction between two substances A and B. Assume that at least one of them is in a form where it is sensible to measure its concentration - for example, in solution or as a gas. For this reaction you could measure the rate of the reaction by finding out how fast the concentration of, say, A was falling per second. You might, for example, find that at the beginning of the reaction, its concentration was falling at a rate of 0.

Read mol dm-3 s-1 as "moles per cubic decimetre or litre per second". This means that every second the concentration of A was falling by 0. This rate will decrease during the reaction as A gets used up. Summary For the purposes of rate equations and orders of reaction, the rate of a reaction is measured in terms of how fast the concentration of one of the reactants is falling.

Its units are mol dm-3 s Orders of reaction I'm not going to define what order of reaction means straight away - I'm going to sneak up on it! Orders of reaction are always found by doing experiments. You can't deduce anything about the order of a reaction just by looking at the equation for the reaction.

So let's suppose that you have done some experiments to find out what happens to the rate of a reaction as the concentration of one of the reactants, A, changes. Some of the simple things that you might find are: The rate of reaction is proportional to the concentration of A That means that if you double the concentration of A, the rate doubles as well.

If you increase the concentration of A by a factor of 4, the rate goes up 4 times as well. You can express this using symbols as: Writing a formula in square brackets is a standard way of showing a concentration measured in moles per cubic decimetre litre.

You can also write this by getting rid of the proportionality sign and introducing a constant, k. The rate of reaction is proportional to the square of the concentration of A This means that if you doubled the concentration of A, the rate would go up 4 times If you tripled the concentration of A, the rate would increase 9 times Generalising this By doing experiments involving a reaction between A and B, you would find that the rate of the reaction was related to the concentrations of A and B in this way: This is called the rate equation for the reaction.

The concentrations of A and B have to be raised to some power to show how they affect the rate of the reaction. These powers are called the orders of reaction with respect to A and B.

For UK A' level purposes, the orders of reaction you are likely to meet will be 0, 1 or 2. But other values are possible including fractional ones like 1.

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If the order of reaction with respect to A is 0 zerothis means that the concentration of A doesn't affect the rate of reaction. Mathematically, any number raised to the power of zero x0 is equal to 1. That means that that particular term disappears from the rate equation.Full Title: Modernizing the E-rate Program for Schools and Libraries Document Type(s): Report and Order, Order Bureau(s): Wireline Competition Description: FCC Modernizes E-Rate Program To Expand Robust Wi-Fi Networks In The Nation's Schools and Libraries.

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Oct 12,  · About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners . Rate and Order of Reactions The rate of a chemical reaction is the amount of substance reacted or produced per unit time.

The rate law is an expression indicating how the rate depends on the concentrations of the reactants and catalysts. Rate Laws and Order of a Reaction.

## Rate law and reaction order (video) | Khan Academy

Determining the Order of a Reaction from Its Rate Law. We need to know the rate law of a reaction in order to determine: The order of the reaction with respect to one or more reactants.

The overall order of the reaction. For the rate law.

Rate and Order of Reactions