[Music] when you're making chemicals commercially the reactions usually make multiple products however there's normally only one or maybe two that are actually useful for example in this reaction the aim is only to make hydrogen so the other product in this case carbon dioxide is basically waste this production of waste products happens a lot in industrial processes and so it's helpful for companies to be able to quantify it and know exactly how much of the reactants are actually going to form the useful products that they want so in this case that would be what percentage of the carbon monoxide and water is actually going to form hydrogen we call this value the atom economy and the official equation for it looks like this so we have to take the relative formula mass of the desired product or products if there are more than one and divide it by the total relative formula masses of all the reactants and then we multiply it all by 100 to turn it into a percentage as the aim of this reaction is to create hydrogen that's our desired product and its mr would be two times one so two for our reactants we have carbon monoxide which has an mr of 28 and water which has an mr of 18. so to get the total emma of all our reactants we just add 28 and 18 together to get 46. so to find the atom economy of this reaction we take our mr of hydrogen because that's our desired product and divide it by the 46 because that's the mr of all of our reactants then finally we multiply the whole thing by 100 to turn into a percentage giving us an atom economy of 4.35 4.35 is actually a pretty low atom economy because it means that only 4.35 percent of the reactants are being turned into the useful product that we want whereas the other 95.65 is being given off as waste in general atom economies are usually much higher than this but they can also be even lower as an example of a reaction with a very high atom economy let's take a look at this one where we have nitrogen and hydrogen reacting together to form ammonia because the desired product ammonia is the only product here the atom economy would be 100 because all of the reactants are being used to make ammonia there aren't any other products that could be considered waste next we need to cover the main reasons why it's important to consider atom economy number one is that raw materials are expensive and so if they're mostly being converted into waste products the process is generally going to be less profitable reason 2 is that it's less sustainable to use large quantities of reactants to make tiny amounts of products and three waste products themselves can be expensive to get rid of and can damage the environment the best solutions to these problems are to either use a more efficient reaction or to find a use for the waste products so that they become a useful by-products instead of waste and even if they can't sell these useful by-products for very much money it's still much better than paying to dispose of the waste the last thing to cover are that there are lots of other important factors to consider when you're thinking about how profitable a reaction is for example the percentage yield the cost of the raw materials the position of the equilibrium the rate of reaction and the cost of maintaining the right conditions like the temperature and the pressure anyways that's everything for today so if you found it useful then please do give us a like and subscribe and hopefully we'll see you again soon