In this introduction are given the explanation of how to find out an empirical formula if one has found out the chemical elements of an unknown substance and measured their ratio of masses. Also, it is described how one can calculate the ratio of masses from a given empirical formula.
Two examples and the explanation of the principles of "how to calculate" are given here.
The empirical formula tells us which sort of chemical elements and how many atoms of every one are necessary to form a chemical substance.
But what can we do with this information?
Here are two examples:
1.) The first point is that we have a chemical compound which consists of more than one chemical element. Let us say rocksalt, NaCl, for example. As we can see there are two elements namely sodium (Na) and chlorine (Cl). Their ratio of number of atoms here is 1:1, i.e. 1 Na and 1 Cl atom.
Since we know that every chemical element's atoms have different masses we can see easily that the MASS ratio of Na and Cl is even NOT 1:1.
So, how can we calculate the mass ratio of these elements in NaCl?
First of all we need the atomic masses of both Na ...
In this introduction are given the explanation of how to find out an empirical formula if one has found out the chemical elements of an unknown substance and measured their ratio of masses. Also, it is described how one can calculate the ratio of masses from a given empirical formula under use of the atomic weights of the elements.
Two examples and a step-by-step explanation of the ways of "how to do" are given here. With these examples a student can understand how to solve this important question for both inorganic and organic compounds.
Finding Formula Based on Neutralization Reaction
Salicylic acid, used in the manufacture of aspirin, contains only the elements carbon, hydrogen and oxygen. Each molecule of the acid contains only one acidic hydrogen. When 1.00g of salicylic acid undergoes complete combustion, 2.23g CO2 and 0.39 g of H2O are formed. When 1.00g of salicylic acid is titrated with 0.100M NaOH, 72.4mL of base is needed for a complete reaction.
a. What is the empirical formula for salicylic acid?
b. What is the molecular formula for salicylic acid?
c. Write a balanced chemical equation for the neutralization of salicylic acid by sodium hydroxide.