Universal Gas Constant Lab. Aim: To determine the universal constant for gases by collecting gas from a neutralization reaction and determining the volume and pressure of the gas and then the partial pressure of the gas formed.

Peter Jr Idoko

11 TF

Aim: To determine the universal constant for gases by collecting gas from a neutralization reaction and determining the volume and pressure of the gas and then the partial pressure of the gas formed.

List of Apparatus:

Ruler ± 0.1cm
Eudiometer Tube ± 0.05cm3
Beaker
Copper wire
Weighing Balance ± 0.001g

Quantitative Observations:

Volume of HCl(aq) used = 10cm3

Concentration of HCl(aq) used = 3M

Required Mass of Mg(s):

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

P(H20) (at 24C) = 3.0 kPa
P(H2) = Ptotal - PH20

= 107.3-3.0=104.3kPa

Volume of H2(g) = 45cm3 = 0.045dm3

Number of moles of H2(g) = (0.045/24) = 0.001875moles

Ratio of Mg(s) to H2(g) = 1:1

0.001875 moles of Mg(s)
0.001875 * 24.305 = 0.0455g ≈ 0.04g

Universal Gas Constant: P.V = n.r.T → r = (P.V)/(n.T)

R = (104.3 * 0.045)/(0.001875 * (24.5+273)) = 8.41 K-1 mol-1
Percentage Error = {(8.41-8.31)/8.31} * 100 = 1.2%

Qualitative Observations:

Colorless gas bubbles observed.
Concentration swirls observed.
Significant effervescence noticed close to the magnesium ribbon.
Colorless gas produced slowly then almost instantaneously the rate at which the colorless gas is being produced speeds up rapidly.
Eudiometer warms ...

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Number of moles of H2(g) = (0.045/24) = 0.001875moles

Ratio of Mg(s) to H2(g) = 1:1

0.001875 moles of Mg(s)
0.001875 * 24.305 = 0.0455g ≈ 0.04g

Universal Gas Constant: P.V = n.r.T → r = (P.V)/(n.T)

R = (104.3 * 0.045)/(0.001875 * (24.5+273)) = 8.41 K-1 mol-1
Percentage Error = {(8.41-8.31)/8.31} * 100 = 1.2%

Qualitative Observations:

Colorless gas bubbles observed.
Concentration swirls observed.
Significant effervescence noticed close to the magnesium ribbon.
Colorless gas produced slowly then almost instantaneously the rate at which the colorless gas is being produced speeds up rapidly.
Eudiometer warms up slightly during the reaction.
Droplets observed above the liquid, also some droplets on the sides of the eudiometer.
The magnesium ribbon diminishes in size.
The magnesium ribbon gets shinier and looks cleaner.
Hydrochloric acid is also noticed flowing out from underneath the eudiometer.

Conclusion:

The literature value of the universal gas constant is 8.31 K-1 mol-1 and my value is 8.41 K-1 mol-1, which implies that the percentage error of my experimental gas constant is 1.2%. Under the conditions in which the experiment was performed, my results are acceptable because very little errors where encountered and the the percentage error is very small. Also due to the fact that the experiment was conducted under the same room temperature and pressure and the same mass of magnesium was used for each trial. A random error which I believe might have affected my result was the droplets noticed on the sides of eudiometer and this is an error because it’s meant to just be the hydrogen gas present there, not the gas and the droplets.

Evaluation:

Improvement:

One major thing that I would do to improve the investigation would be to do more trials for the experiment, thus to reduce the random errors.
To clean the eudiometer very well, and ensure that there’s as little as possible dirt and impurity present in the eudiometer.

Bibliography:

IB Chemistry. (2009). Course Details, Data Booklet and Internal Assessment Related Documents.