You know (or are told) that they are oxidised to iron(III) ions. Now you repeat this for the iron(II) ions. The final version of the half-reaction is: That's easily put right by adding two electrons to the left-hand side. The left-hand side of the equation has no charge, but the right-hand side carries 2 negative charges. In the chlorine case, all that is wrong with the existing equation that we've produced so far is that the charges don't balance. Hydrogen ions (unless the reaction is being done under alkaline conditions - in which case, you can add hydroxide ions instead) Now you have to add things to the half-equation in order to make it balance completely. If you forget to do this, everything else that you do afterwards is a complete waste of time! The first thing to do is to balance the atoms that you have got as far as you possibly can:ĪLWAYS check that you have the existing atoms balanced before you do anything else. In the chlorine case, you know that chlorine (as molecules) turns into chloride ions: You start by writing down what you know for each of the half-reactions. In building equations, there is quite a lot that you can work out as you go along, but you have to have somewhere to start from! You would have to know this, or be told it by an examiner. In the process, the chlorine is reduced to chloride ions. In reality, you almost always start from the electron-half-equations and use them to build the ionic equation.Įxample 1: The reaction between chlorine and iron(II) ionsĬhlorine gas oxidises iron(II) ions to iron(III) ions. That's doing everything entirely the wrong way round! In the example above, we've got at the electron-half-equations by starting from the ionic equation and extracting the individual half-reactions from it. Working out electron-half-equations and using them to build ionic equations
Note: If you aren't happy about redox reactions in terms of electron transfer, you MUST read the introductory page on redox reactions before you go on. These two equations are described as "electron-half-equations" or "half-equations" or "ionic-half-equations" or "half-reactions" - lots of variations all meaning exactly the same thing!Īny redox reaction is made up of two half-reactions: in one of them electrons are being lost (an oxidation process) and in the other one those electrons are being gained (a reduction process). This shows clearly that the magnesium has lost two electrons, and the copper(II) ions have gained them. You can split the ionic equation into two parts, and look at it from the point of view of the magnesium and of the copper(II) ions separately. There are links on the syllabuses page for students studying for UK-based exams. You should be able to get these from your examiners' website. How do you know whether your examiners will want you to include them? The best way is to look at their mark schemes. Practice getting the equations right, and then add the state symbols in afterwards if your examiners are likely to want them.
This topic is awkward enough anyway without having to worry about state symbols as well as everything else. Note: I am going to leave out state symbols in all the equations on this page. When magnesium reduces hot copper(II) oxide to copper, the ionic equation for the reaction is: Take your time and practise as much as you can. It is a fairly slow process even with experience. This is an important skill in inorganic chemistry.ĭon't worry if it seems to take you a long time in the early stages.
#Ionic equation calculator how to#
This page explains how to work out electron-half-reactions for oxidation and reduction processes, and then how to combine them to give the overall ionic equation for a redox reaction. WRITING IONIC EQUATIONS FOR REDOX REACTIONS Absolute Vs.Writing ionic equations for redox reactions.For questions or remarks please contact us. Warning: Lenntech BV cannot be held responsible for errors in the calculation, the program itself or the explanation. Lenntech can advise you which is most appropriate. Contactįor every different application of water conditioning specific ion exchange resins ( Rohm & Haas / Lanxess / Purolite) are available. You cannot send data if you don't give your name, country, Phone and Email. Please fill in the filed in the table Contact Information. You can send the values in the calculator to Lenntech to determine the best resin for your application. Input fields marked with * are required to give good calculated values. As a consequence this calculator ONLY gives you an indication about the different parameters that are necessary to design an Ion Exchange water treatment installation. The calculations are made using theoretical equations. The calculator is based on the following process: This calculator helps you with the design of a ion exchange installation. Home > Calculators > Ion exchange calculator for one chemical element Ion exchange calculator
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