Question

data provided

Table 2. Experimental Data Trial 1 Trial 2 Trial 3 30.13 Atmospheric Pressure (inches Hg) Mass Mg used (6) 0.039 0.025 0.011 Volume Hz gas generated (mL) 39.58 25.89 11.47 Water Temperature (°C) 19.0 19.0 19.0 16.48 16.48 16.48 Partial Pressure Water Vapor (mm Hg: from Table 1) Difference in Water Levels (mm) 14.31cm 35.72cm 46.13cm Table 3. Molar Gas Volume and Ideal Gas Constant Calculations Trial 1 Trial 2 Trial 3 Trial 3 765.3 16.48 16.48 16.48 Atmospheric Pressure (mm Hg)* Partial Pressure Water Vapor Vapor (mm Hg; copy from above) Partial Pressure Liquid Water (mm Hg) Partial Pressure H2 (mm Hg) 10.5 26.3 33.9 738.32 722.52 714.92 Water Temperature (K) 292 292 292 Standard Volume H2 (ml)" 35.7 22.9 10.0 Moles Mg used (mol)* 1.605 x 10-6 1.029 x 10-6 4.526 x 107 Moles Hz produced (mol)* 1.605 x 10° 1.029 x 103 4.526 x 104 Molar Volume (4/mol) 24.92 24.29 24.30 24.5 Average Molar Volume (L/mol)* Ideal Gas Constant (L:atm)/(mol:(0)* Average Ideal Gas Constant ((Leatm)/(mol:K)* 0.07398 0.07243 0.07167 0.0727

please solve Q5 & Q6

Q4 answer

Answer 1

5)

Precision = How close the measured values are to each other

Standard deviation is one method to determine the precision of a set of measurements.

Deviation = Actual value - experimental value

Ideal gas constant

For trial one, Deviation, D1 = 0.08206- 0.07398 = 0.00808

trial two, D2 = 0.08206-0.07243 = 0.00963

trial three, D3 = 0.08206-0.07167 = 0.01039

Standard deviation, S.D. = (D1 + D2 + D3)/No. of measurements = (0.00808 + 0.00963 + 0.01039)/ 3 = 0.00937

All of the data points lie within two standard deviations.

Molar Volume

Trial one : D1 = 22.414 - 24.92 = -2.506

Trial two: D2 = 22.414 - 24.29 = -1.876

Trial three : D3 = 22.414 - 24.30 = -1.886

S.D. = (D1 + D2 + D3)/3 = 2.089

All of the data points lie within two standard deviations.

Accuracy : How close the measured values are to the actual/conventional/reference value.

The % error calculated in Q4 denotes the accuracy in the molar volume and ideal gas constant values from experiment.

In both, ideal gas constant and molar volume measurements, the deviations from the actual value are all positive and all negative, respectively. This indicates a sytematic error in which all the measured values show deviation from the actual value in the same direction ( either up or down ).

Typical sources of systematic error include:

a) observational error

b) instrumental error

c)environmental interference e.g. temperature

6)

Partial pressure of H2 (mm Hg):

765.3 - 10.5 = 754.8

Water Temperature (K) :

190C + 273 = 292

Standard Volume H2 calculation (mL) :

754.8 * 39.58/292 = 765.3 * V2/273

V2 = 36.50

Moles of Mg used = 0.039/24 = 1.605 * 10-3

Moles of H2 produced = moles of Mg used = 1.605 * 10-3

Ideal gas constant = partial pressure of hydrogen * Volume of hydrogen /( No. of moles of hydrogen * Temperature of water )

= 0.993 atm * 0.040 L /( 0.001605 mol * 292 K) = 0.0847

% error in ideal gas constant = ( actual - experimental) * 100/ actual = (0.08206-0.0847)*100 / 0.08206

= - 3.28 %

Molar volume (L/mol) = 0.040/ 0.001605 = 0.03650 / 0.001605 = 22.47

% error in molar volume = 0.25

In this particular experiment, the Dalton's law correction doesn't improve the accuracy of measured ideal gas constant or the molar volume.