This online Chemical Reaction Calculator checks whether a given chemical equation is balanced and finds the appropriate stoichiometric coefficients. It also calculates the amounts of reactants and reaction products in both moles and grams. In addition, the amount of unreacted reagents and the limiting reactant are determined. The chemical reaction equation may include free electrons and electrically charged molecules (ions) as well as hydrated compounds.
You can enter a chemical equation manually or paste the equation copied from a web page or text document (including DOC or PDF file). The indices are denoted using <sub> and </sub> html tags (e.g. H2O) or with the help of the ‘tiny’ numbers, like ₂ or ₅ , (e.g. H₂O) which then automatically converted to normal form. In a hydrated compound the middle dot (·) or the asterisk (*) precedes the water formula (e.g. CuSO4·5H2O). In what follows is a more detailed syntax guide to our calculator.
After you click the ‘Calculate’ button, the equation is automatically balanced and a list of all reactants and reaction products involved in the chemical reaction appears. In case the original equation was unbalanced, the field with this equation is highlighted in light pink.
To calculate the amount of reagents you need to take to get a certain amount of a given reaction product, enter that amount either as the number of moles or as its weight in grams in the corresponding field and then press the ‘Enter’ key.
If you enter in the corresponding fields the amounts of reagents, either as number of moles or weight in grams, then, after pressing the ‘Enter’ key, you will get the amounts of reaction products (in moles and grams). In addition, the amounts of unreacted reagents are calculated and the limiting reactant is determined. The field with the limiting reactant is highlighted in pink.
Chemical Reaction Calculations
The chemical reaction equation shows which substances react with each other and in what quantities, as well as what substances are formed and how much of each can be obtained.
Substances enter into chemical reactions in quantities proportional to the coefficients in the chemical equation. This means that the ratio of the amounts of reactants (in moles) is equal to the ratio of the corresponding coefficients in the reaction equation.
When solving chemical calculation problems using reaction equations, the following algorithm can be used:
1) Write an equation for a chemical reaction and balance it.
2) Convert the problem data (mass, volume) to the amount of substance (moles).
3) Find the amounts of reaction products according to the coefficients in the reaction equation.
4) Convert the found amounts of substances into mass (volume) according to the condition of the problem.
Our Chemical Reaction Calculator implements the above algorithm and helps you solve most chemical problems in seconds without resorting to time-consuming calculations.
So, the first step in chemical reaction calculations is balancing chemical equations. This means looking for stoichiometric coefficients for the reactants and products. It’s important because in a chemical reaction, the quantity of each element does not change (the law of conservation of mass). Thus, each side of the equation must represent the same quantity of atoms of any chemical element. In case of ionic reactions, the same electric charge must be present on both sides of the equation.
There are a number of methods for balancing chemical equations. But in case of complex reactions involving many compounds, it is preferable to balance equations using algebraic methods, based on solving set of linear equations.
Our calculator uses the Gauss-Jordan elimination algorithm for solving set of linear equations. The method is modified for finding integer coefficients.
Next, we have to find the amounts of reactants and/or reaction products. For any balanced chemical equation, we know the stoichiometric coefficients that show the amounts (in moles) of both the reactants and products. Knowing the molecular weight of the compounds involved in the reaction, it is easy to find the mass of these compounds in grams.
How to find limiting reactant
If the masses of several substances entering the reaction are known, then the question arises: which substance determines the amount of products obtained. Obviously, the amount of products should be determined by the substance that is completely consumed, with the other reactants remaining in excess. Such a substance is called the limiting reactant.
To find out which substance reacts completely, it is necessary to compare the amounts of the reactants with the corresponding coefficients in front of the formulas of the substances in the reaction equation. For each substance, you can find the coefficient of proportionality of its amount to the value of the corresponding stoichiometric coefficient. The substance with the least coefficient of proportionality is, obviously, the limiting reactant.
Syntax Guide
• Reactants and products in a chemical reaction are separated by an equal sign (=). The substances are separated by a plus sign (+).
• The formula of a substance should be entered using the upper case for the first character in the element’s name and the lower case for the second character (compare: Co – cobalt and CO – carbon monoxide).
• Indices should be entered as normal numbers after the appropriate elements or groups, e.g. H2O for a water molecule or (NH4)2SO4 for ammonium sulfate.
• Parentheses ( ), square brackets [ ] and braces (curly brackets) { } can be used in the formulas. Nested brackets are also allowed, e.g. [Co(NH3)6]Cl3. The degree of nesting is unlimited but all the brackets should be balanced.
• In a hydrated compound the middle dot (·) or the asterisk (*) must go before the water molecule formula (e.g. CuSO4·5H2O).
• To denote an ion specify its charge in curly brackets after the compound: {+2} or {2+}. Example: H{+}+CO3{2-}=H2O+CO2.
• To include an electron into a chemical equation use {-}, e.g. Fe{+3}+{-}=Fe.
• Do not enter the state of compounds such as solids (s), liquids (l) or gases (g).
Using Chemical Reaction Calculator
When entering a chemical equation manually or pasting the copied equation it converts automatically to the ‘normal’ form according to the above rules. All the spaces are ignored and symbol → is converted to =. But symbols ↑ and ↓ remain in place.
Note, that both indices and charges can be denoted in the source document using <sub></sub> and <sup></sup> html tags, e.g. SO4-2, or denoted using the ‘tiny’ symbols, e.g. SO₄⁻². They are also converted automatically to the ‘normal’ form.
A single electron can be denoted as e– (e<sup>-</sup>) or e⁻ (with ‘tiny’ minus).
Output format
Using the appropriate drop-down menu one can choose an output format for the balanced chemical equation:
• Html – The balanced equation is represented using html tags for indices and charges. A single electron is denoted as e–. Clicking the ‘Copy to clipboard’ button ( ) you can copy the result ‘as is’, including all the tags, and then you can paste it into any html-page. However, clicking Ctrl-A and Ctrl-C you can copy the result without the tags and paste it into a DOC document keeping duly formatted indices and charges.
• Small indices – The balanced equation is represented using ‘tiny’ symbols for indices and charges. For example, CO₃²⁻ where unicode characters are used: ₃ = (\u2083), ² = (\u00B2), ⁻ = (\u207B). A single electron is denoted as e⁻.
• Normal – The balanced equation is represented according to the above syntax guide.
Error notifications
There are a number of obvious notifications in case of error detected in the course of initial inspection of the entered equation, like Unexpected character or Brackets not balanced. The following notifications deserve special attention:
Improper equation – The entered equation has chemical elements on the left hand side that are missing on its right hand side, or vice versa.
Impossible reaction – The entered equation represents an impossible reaction. For example, the equation (NH4)2SO4=NH4OH+SO2 has only trivial solution when all the coefficients set to zero.
Multiple independent solutions – The entered equation can be balanced in an infinite number of ways. Usually it is a combination of a few different independent reactions. For example, the equation H+O=H2O+HO has no unique solution because, for instance, two solutions are 3H+2O=H2O+HO and 4H+3O=H2O+2HO which are not multiples of each other. The equation can be separated as H + O = H2O and H + O = HO, each of which does have a unique solution.
Element “…” doesn’t exist – An element’s name, entered in accordance with the above syntax guide, does not indicate a real chemical element. Sometimes an immutable group in chemical compounds is replaced with fictitious element to balance the equation which otherwise can not be uniquely balanced. In this case, our calculator will balances the chemical equation but will not compute the reaction stoichiometry.
Examples of Chemical Reactions
Example 1. Find the amount of reagent
When calcium carbonate reacted with nitric acid, 5.6 liters (at 1 atmosphere of pressure and 0 °C) of carbon dioxide were released. What is the mass of the calcium carbonate that reacted?
Solution
1) Let’s write the reaction equation:
Then, copy the above equation as it is and paste into the ‘Chemical Equation’ field of the Chemical Reaction Calculator. It immediately converts to the ‘normal’ form. Then click the ‘Calculate’ button. In the ‘Balanced Equation’ field you will have the result:
The ‘Chemical Equation’ field in the calculator is now highlighted in light pink, indicating that the equation we entered was unbalanced.
2) Now, convert the volume of CO2 into the amount of substance (moles). Note that under the conditions stated in the problem, one mole of any gas, considered ideal, occupies a volume of approximately 22.4 liters (the so-called molar volume). So, the amount of CO2 equals to: (5.6 L) / (22.4 L/mol) = 0.25 mol.
3) And finally, we enter the amount of CO2 0.25 mol in the corresponding field in the list of reaction products that appeared in our calculator, and press the ‘Enter’ key. The amounts of all substances involved in the reaction are instantly calculated. And we see that 0.25 moles or 25.02172 grams of CO2 are formed.
Example 2. Limiting reactant problem
Find the limiting reactant if 95.7 grams of C2H3Br3 were reacted with 54.9 grams of O2 and the reaction equation is as follows:
Solution
1) Copy the above equation and paste it into the ‘Chemical Equation’ field of the Chemical Reaction Calculator, then click the ‘Calculate’ button. In the ‘Balanced Equation’ field you will see the balanced equation. Now the ‘Chemical Equation’ field in the calculator is not highlighted in light pink, indicating that the equation we entered was already balanced.
2) Next, we enter the given amounts – 95.7 grams of C2H3Br3 and 54.9 grams of O2 – in the corresponding fields in the list of reactants that appeared in our calculator, and press each time the ‘Enter’ key. The amounts of all substances involved in the reaction are instantly calculated, and we can see that the field with C2H3Br3 is highlighted in pink, indicating the limiting reactant.
As the calculation results show, C2H3Br3 reacted completely, but out of 54.9 grams of oxygen, almost 23.33 grams did not react. So, as we see, C2H3Br3 is the limiting reagent, and O2 is the excess reagent.
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