Molar Mass Lab Report

Determination of the molar mass of a chosen compound/element

Fran Jurinec 1.M
Introduction
Molar mass is a physical property of a chemical element or substance which shows the mass per amount of substance. My task is to determine the molar mass of a product substance from one of the following equations:
a. Zn(s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g)
b. CaCO3 (s) + 2HCl(aq) → CaCl2 (aq) + CO2 (g) + H2O(l)
c. Na2SO3 (aq) + 2 HCl (aq) → 2NaCl (aq) + S (s) + SO2 (g)
For my experiment, I chose to determine the molar mass of SO2, which is a product from the 2nd equation. For this experiment I have determined the independent, dependent and controlled variables and they are:
Independent variables: Volume of HCl used [ V(HCl) ]
Dependent:

Since the product I am investigating is in gaseous state, I will also have to use the formula: pV = nRT in which p is pressure (Pa), V is volume (m3), n is molar quantity (mol), T is temperature (K) and R is the gas constant which is 8.314 J/kmol.
Research question: What is the molar mass of SO2 and does it depend on the volume of HCl used in the reaction?
My hypothesis is that the molar mass of SO2 [ M(SO2) ] will be around 60-70 g/mol based on my previously gained knowledge of the molar masses of Sulphur (~32Da) and Oxygen (~16Da) which I got from the periodic table of elements. Also I believe that it will not depend on any other factor because molar mass is a constant property of a substance or element and does not

Now we place into the Erlenmeyer flask filled with Na2SO3 (aq), 30ml of 0.3 mol/L solution of HCl.
6. Right after mixing the two solutions, we quickly put the cap on the flask so that all of the gas produced is transferred through the glass tubes into the measuring cylinder.
7. After we see that the reaction is complete, we can read the measurements from the thermometer, pressure gauge and measuring cylinder to get the mass, temperature and pressure which we will need for later calculations.
8. We now repeat this entire process 2 more times. The second time we use 50ml of the HCl solution, and the third time we use 70ml of the solution.
Calculations steps:
1. We must now use the pV = nRT formula in order to get the molar mass (n) of SO2. For this we require all of the other variables which we got from the experiment which are the temperature, pressure and volume, but we also know the R constant which equals 8.314 J/kmol.

2. We can now rearrange the equation in order to make it easier to calculate only n.

3. After rearrangement the formula should look like this: n(SO2) = pV/RT

4. Now we just put in all of the known values for pressure, temperature, volume, and the gas constant and calculate the molar mass of SO2.

Picture 1: Diagram of