Q&A for How to Balance Chemical Equations

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  • Question
    How did the oxygen became 7 when 3x2 is 6? Do you always add one?
    Community Answer
    You get 3x2=6 oxygen atoms in the carbon dioxide, but at this stage there is also 1 oxygen atom in the water. So, 6+1=7.
  • Question
    How can I balance NaCl + AgNO3 -> AgCl + NaNO3?
    Community Answer
    This equation is already balanced when using the first method (traditional balance) in the article.
  • Question
    What causes the color of copper sulphate to change when an iron nail is dipped into it?
    Community Answer
    When iron (Fe) and copper sulphate (CuSO4) solution react, they undergo a single displacement reaction, also known as a substitution reaction, to form solid copper (Cu) and aqueous iron sulphate (FeSO4). The iron can be solid or aqueous but the copper sulphate must be aqueous in order to facilitate the reaction.
  • Question
    How can I balance Na2CO3 + HCl -> NaCl + H2CO3?
    Community Answer
    First multiply NaCl by 2, since you have 2 Na on the reactant side. Na2CO3 + HCl -> 2NaCl + H2CO3. Then, since there are now 2 Cl in the product side, multiply HCl by 2. This also has the effect of balancing the hydrogen, and the equation is now balanced as Na2CO3 + 2HCl -> 2NaCl + H2CO3.
  • Question
    How do I balance hgo = hg+o2?
    Community Answer
    HgO -> Hg + O2. Multiply the left side by 2 to get 2 Oxygen. 2HgO -> Hg + O2. Then multiply Hg on the right by 2. Et voilà! We get the balanced 2HgO -> 2Hg + O2.
  • Question
    On step 7 it says you now have 6 oxygen atoms in the carbon dioxide molecule do I times the 3 to get 6?
    Community Answer
    Yes. You multiply the subscript by the number that was put out in front. So CO2 has one carbon and two oxygen atoms (pretend the 2 is subscript), while 3(CO2) has 3 carbon and six oxygen atoms. If it helps (and again, pretend that all the numbers in this equation are subscript), CO2=C1O2. You always multiply the number in front by the subscript and if there is none, it means that the subscript is equal to 1.
  • Question
    How can we assume a=1. It can be anything right?
    Community Answer
    It is a balanced equation. We don't assume anything, the writer chose to give you the answer of "a" for use in this example. If you did not know a=1, then it could theoretically be anything.
  • Question
    Why does a = c for the algebraic method?
    Community Answer
    According to the law of conservation of mass, the amount of P will be the same on both sides. So the amount of P as a reactant (a), will be the same as the amount of the product of P (c).
  • Question
    What is the action of diluted nitric acid on magnesium?
    Community Answer
    Magnesium will react with diluted nitric acid to produce magnesium nitrate and hydrogen gas.
  • Question
    Is the algebraic way or the traditional way faster?
    Community Answer
    It depends what you are most comfortable with. After some practice, you could even do this all in your head.
  • Question
    How will I know what to balance?
    Community Answer
    You balance the atoms of the same chemical that are not equal.
  • Question
    How do I balance a chemical equation where one element occurs only on one side?
    Community Answer
    That is impossible, due to the Law of Conservation of Mass there must be equal masses of each atom on both sides of the equation.
  • Question
    How did the number of Oxygen become 10 when you add 4 with 7?
    Community Answer
    The 7 is the addition of the 3X2 oxygen atom and the single oxygen atom. So when you don't add 4 and 7 you add 4 and 6. The single atom has become 4 so if you take the single of the 7 and add the 4 you get 10. (3x2=6 6+4=10)
  • Question
    Is this correct? Mg + O2 = 2MgO.
    Top Answerer
    This should be 2Mg + O2 = 2MgO. Magnesium metal reacts with oxygen in a diatomic form to produce magnesium oxide in the basic form of Mg + O2 = MgO. Count how many atoms there are on each side of the equation for both oxygen and magnesium; the number of each of the atoms should be the same on both sides of the equation. That will guide you to put the correct coefficients.
  • Question
    How do I know when a chemical equation is unbalanced?
    Community Answer
    Count the number of atoms in each side. For e.g: the equation Na + HCl -> NaCl + H2, on the left side, Na is 1, H is 1 and Cl is 1, on the right side, Na is 1, Cl is 1 but H is 2, so this is an unbalanced equation.
  • Question
    How do I determine what the reactive side of the equation is?
    Community Answer
    In a chemical equation, there are reactants and products. The products are what the reactants develop after going through a chemical process. Reactants are usually on the left-hand side of an equation.
  • Question
    Is it always that when balancing, the elements on the left side must have the same numbers on the right?
    Top Answerer
    Yes. There should always be the same amount of each element on either side of the equation. That's what makes it balanced!
  • Question
    Who developed chemical equations?
    Community Answer
    The first chemical equation was invented by Jean Beguin in 1615.
  • Question
    How do I write the state of matter in a chemical reaction?
    Community Answer
    Write the state of matter after writing the chemical formula as subscript in parentheses. For example, for liquid water this would be H2O(l), where the l and 2 are subscript.
  • Question
    How do I apply algebraic method when balancing in an acidic/basic medium?
    Community Answer
    I think the medium doesn't matter as far as the acid/ base does not play a role in the reaction. In that case, you should proceed exactly as shown. If the acid/base plays a role in the reaction then you must know the acid/base/salt involved and proceed regardless the pH or acidity.
  • Question
    How can I form an equation?
    Community Answer
    Adding an element, compound or mixture to another one forms the reactant side. Then, to form the product side, separate the compound or mixture and replace part of it with the other elements or let it stand alone.
  • Question
    Why does step six say that there are ten oxygen atoms on the right side of the equation?
    Community Answer
    There are four oxygen atoms in the 4H2O component and six oxygen atoms in the 3CO2 component, which makes ten oxygen atoms in total.
  • Question
    My teacher recently gave me an "F" for writing a "1" as a lead coefficient for compounds that did not need a larger digit coefficient. Am I wrong when I balance a chemical equation and use a "1"?
    Top Answerer
    You are not technically wrong, although people leave out the 1 because when you don't write any coefficient, everyone understands that there is a coefficient of 1 anyway. So leave it out next time to prevent confusion. You may have also balanced the equation incorrectly; check with your teacher on why she gave you the bad mark.
  • Question
    How do I balance KOH + H3PO4 -> K3PO4 + H2O?
    Community Answer
    Using the algebraic method described above produces a result of 3KOH + H3PO4 -> K3PO4 + 3H2O.
  • Question
    What is a balance equation of BaCl2 +Na2SO4= BaSO4+ NaCl?
    Community Answer
    BaCl2 + Na2SO4 = BaSO4 + 2NaCl. Just multiply the Sodium and Chlorine on the left side by 2.
  • Question
    How do I know if it is balanced correctly or not?
    Community Answer
    Chemical reactions cannot create, destroy, or change the atoms that enter the reaction. Chemical reactions can only rearrange the reactant atoms into new molecular structures. Since atoms (mass/matter) are always conserved, an equation is balanced when the same number of each specie of atoms appears on each side of the "before-and-after" arrow.
  • Question
    How can I balance the equation "Zn+HCL-Zn Cl2+H2"?
    Community Answer
    "Zn + 2HCl --> ZnCl2 + H2". Balance the equation by multiplying the Cl on the left by two to get the 2Cl found on the right side of the equation in ZnCl2. Then check for the rest to ensure that the number of Zn, Cl, and H on each side of the equation is the same.
  • Question
    Where can I find more examples of equations being balanced?
    Community Answer
    Try doing a simple internet search or look for lessons online.
  • Question
    When balancing an equation, do I consider each atom in a polyatomic ion or consider the entire thing as an 'atom' on its own with its own charge?
    Community Answer
    Look at how many of each atom there is on each side of the equation and do basic math to make all elements even on both sides.
  • Question
    PCl5 + H2O --> H3PO4 + HCl: Help me how to it balance?
    Community Answer
    PCl5 + 4H2O --> H3PO4 + 5HCl. You may want to balance chlorine first. Worry about the oxygen last.
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