Behaviour of Gases

Experiment 2

Behavior of Gases

PURPOSE
This experiment has two parts. The purpose of part A of the experiment is to determine the atomic mass of a metallic element whereas the purpose of part B of the experiment is to determine the rate of diffusion of both gases hydrogen chloride and ammonia by measuring the distances travelled by the two gases in the same time period.
For part A the reaction of the metal with the aqueous acid is as follows:
M(s) + n H3O+ -----> M+n(aq) + n/2 H2(g) + n H2O

EQ.1

EQ. I

or,
M + 2HCl -----> MCl2 + H2


For part B the relative rate of diffusion of two different gases at the same temperature is given by the relationship: r1 /r2 = (M2 / M1)1/2

Once the two different gases meet, in this case they are HCl and NH3 ammonium chloride will appear,
HCl(g) + NH3(g) ------> NH4CL(s) !

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EQ. I1

EXPERIMENTAL METHODS
Please refer to the Poe, Judith CHM110F course manual, experiment 2: Behavior of Gases on page 42 - 46.
No deviations were made.
RESULTS
PART A:
1. given:

- density of solution = 1.00 g/mL 

- density of mercury = 13.6 g/mL 
 required: - hydrostatic pressure in torr?
 solution:
Since, psolutionΔh = pHghHg 
 then phydrostatic = hHg

hHg = psolutionΔh/pHg
 hHg = (1.00 g/mL)(326 mm)/13.6 g/mL

= 23.97 torr

2

2. given:

- vapour pressure of H2O = 19.8 torr
PH2 + PH2O = Patm - Phydrostatic 

PH2 = Patm - Phydrostatic - PH2O

PH2 = 760.4 - 23.97 - 20 torr

PH2 = 716.63 since the total pressure of the gas trapped in the burette is: PH2 + PH2O
716.63 + 19.8 = 736.43 torr

Figure 1. Pressure dependence on Temperature

P corresponding to temperature at which the experiment was done at is 20 torr.
3. Referring to question 4, the total pressure - pressure of water = 716.43 torr. 


4.

PH2V = nH2RT

PH2V/RT = nH2

References: 1. Anonymous. Classic Chemistry Experiments : The determination of relative atomic mass. http://www.rsc.org/learn-chemistry/resource/res00000401/the-determination-of-relative-atomic-mass (accessed October 16, 2013). 2. Bouman, A. Lab hints or adjustments for Atomic mass of Magnesium. http://bouman.chem.georgetown.edu/general/magnesium.htm (accessed October 16th 2013) . 3. Anonymous. Determination of Relative Atomic Mass. http://www.nuffieldfoundation.org/practical-chemistry/determination-relative-atomic-mass (accessed October 16, 2013). 4. 1. AnonymousMolar Mass and the Ideal Gas Law Prelab. http://chemistry.bd.psu.edu/aronne/chm111iglMM.pdf (accessed October 18, 2013). 6