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Secondary IV • 2yr.


I'm having trouble balancing chemical equations. Could you give me something, please?

Thank you so much!


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Explanations (1)

  • Explanation from Alloprof

    Explanation from Alloprof

    This Explanation was submitted by a member of the Alloprof team.

    Team Alloprof • 2yr.



    Thank you for your question.


    Before we start, we must understand that we must apply the law of conservation of matter, that is to say, that we must find the same amount of atoms of each element on either side of the chemical equation.


    To properly balance the chemical equations, it is essential that you respect these rules:

    1. The molecules of reagents and products must not be modified. You can't add an atom to them or change the coefficient to balance the equation.
    2. Do not remove or add molecules.
    3. It is unnecessary to write the coefficient when it has a value of 1. If there is nothing in front of an atom/molecule, we imply that the coefficient is 1.
    4. The coefficients must be whole numbers (2,3,4,...), and they must be the smallest possible. If coefficients are fractions, you must multiply by the largest denominator to get only whole numbers.
    5. It is always necessary to check if the equation is well balanced by carrying out the balance of the atoms at the end.


    One of the easiest ways of balancing equations is to start with the most complex molecule.


    Let’s use the equation below as an example! 


    C3H8 + O2 → H2O + CO2

    First, you have to identify the most complex molecule. In this case, C3H8 is the most complex molecule since it is the most complex molecule.


    Second, you have to tally how many of each element there are on each side of the equation. Let's start with carbon. We have 3 atoms of carbon on the reactants' side and only one on the product side, so we must multiply the CO2 by 3. Let's move on with the hydrogen. There are 8 atoms on the left side and 2 on the right side. Therefore, you must multiply the water molecule by 4 to get as many on each side. Then, only oxygen remains to be balanced. There are 2 atoms of oxygen on the products' side and 10 ( (4 on H2O, and 6 on CO2) on the reagents' side. It is, therefore, necessary to multiply the dioxygen by 5 to reach equilibrium giving the following equation:

    C3C8 + 5O2 → 4H2O + 3CO2


    Finally, if we tally the number of atoms on each side of the equation to check that our equation is correct, we get 3 carbon atoms, 10 oxygen atoms, and 8 hydrogen atoms on each side.

    If you have any other questions, don't hesitate! 😊

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