Mole Ratios in a Chemical Reaction

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Renee Buettel

Period D4

Ms. Parziale


Lab #10: Mole Ratios in a Chemical Reaction

Paul Bergin


The main objective of this lab experiment was to balance the given chemical equation and to find the correct mole-to-mole ratio of it.  The theoretical balanced equation was Pb(NO3)2(aq) + K2Cr2O7(aq)  PbCr2O7(s) + 2KNO3(aq). In addition, the ratio of moles was one to one.and the correct mole-to-mole ration was one to one. The experimental results matched this ratio. The theory that was proven was that balancing equations give the correct mole ratio of a chemical equation.


In a chemical equation, there are two sides. The chemicals on the tail end are called the reactants and the chemicals on the other side are called products. An example of this given by Coefficients (2008) is 2H2 + O2 → 2H2O. In this example, “2H2 + 02” is the reactants and “2H2O” is the product. Also, “→” is the sign for “yield.” The big 2s in front of H2 and H2O are called coefficients. In this case, the first 2 indicates that there are 2 molecules of H2, which also means that there are 4 atoms of hydrogen in the reactant part of the equation. The other 2 signifies that there are 2 molecules of H2O as the product. This means that every molecule of H2O that contains 2 atoms of hydrogen contains 4 hydrogen atoms and 2 oxygen atoms. According to Chemistry Formulas (2005), the subscripts are used to signify the number of atoms of an element in a compound. In this example, O2 means that there are 2 atoms of oxygen.

To balance an equation, How can (n.d.), says that an element inventory is first made. For example, if there was the equation H2 + O2 → H2O, it would be written down that on the left side there are 2 hydrogen and 2 oxygen, and on the right side there are 2 hydrogen and 1 oxygen. This is determined by the subscripts.  Next, the guess and check method is used to determine the correct coefficients. When doing this, the inventory is updated.

        A common chemical reaction is a precipitation reaction. As explained by (McGraw-Hill. (n.d.), this reaction involves two ore more solutions combining and resulting in an insoluble product. This reaction happens because of strong attractive forces that certain ions have for each other, which combine and fall out of the solution in the form of a solid. When two aqueous solutions combine and form a solid, precipitate is formed.

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        As explained by Zahm (2008), a mole ratio is used to find an amount of a chemical from a known amount of another chemical. For example, if someone needed to know how much nitrogen is required to react with 9 moles of hydrogen, a ratio would be set up that looks like this:

N2  :  1 =  x

 H2    3      9

When x is solved, it shows that 3 moles of nitrogen are required to react with 9 moles of hydrogen. N2 represents the unknown, H2 represents the known, 1 represents the amount of the unknown, and 3 represents the ...

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