Butane Lab PDF

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Butane Lab...

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Chemistry 20 Lab: Determining the Molar Mass of Butane Problem: What is the experimental molar mass of butane gas, C4 H10? Data collection: Table 1.1: Data collected to determine molar mass of butane gas(C4 H10) using water displacement method Trial number

Trial 1

Trial 2

Trial 3

Initial mass of lighter (g)

14.78

14.74

14.70

Final mass of lighter (g) 14.74

14.70

14.58

Volume of gas collected (mL)

31.00

42.00

50.00

Ambient Room Temperature (℃)

24.00

22.00

22.00

Ambient Room Pressure (cmHg)

66.97

66.97

66.97

Qualitative Data:

-

-

-

Calculations: Average initial mass of lighter: 14.78g +14.74g +14.70g T rial 1+T rial 2+T rial 3 = =14.74 g 3 3 Average Final mass of lighter: 14.74g +14.70g +14.58g T rial 1+T rial 2+T rial 3 = = 14.67 g 3 3

The cylinder filled with butane gas, because the bubbles floated up to the top of the cylinder. Some of the bubbles escaped the graduated cylinder, and went into the surrounding water. The water is a colourless, clear liquid Butane Gas, appears to be colourless. As the cylinder was being filled with butane gas, it began to feel slightly heavier due to the mass of the butane that was added

Average volume of gas (L): T rial 1+T rial 2+T rial 3 mL+50.00mL = 31.00mL+42.00 = 41.00 mL 3 3 1L 1000mL

41.00mL ×

= 0.041 L

Average Ambient Room Temperature (℃): T rial 1+T rial 2+T rial 3 = 24.00℃+22.00℃+22.00℃ = 22.67 ℃ 3 3 Ambient Room Pressure (mmHg): 66.97cmHg 10mmHg 669.7mmHg × 1cmHg = × 1 1

101.325kP a 760mmHg

= 89.29 kPa

Calculation for molar mass determined by water displacement method: 1. m= average final mass-average initial mass= 14.74g-14.67g= 0.07000g n= ? P=89.29 kPa T=22.67 ℃+273.15K= 295.82K V=0.041 L a×L R= 8.314 kP mol×K Using Ideal Gas Law PV=nRT n= PRTV n=

(89.29 kP a)(0.041L) a×L (295.82K)(8.314kPmol×K

n=0.001489 mol M=

m n

=

0.07000g = 0.001489mol

47.03 g/mol

2. Actual Molar Mass of Butane: Molar mass C4H10= (4 mol C × 12.01g) + (10 mol of H × 10.00g)= 58.14 g/mol C4H10

Errors and Improvements: | experimental −accepted| × 100% = accepted

|47.03g /mol−58.14g /mol| 58.14g /mol

× 100% = -19.11% error

Table 1.2- Errors and improvements for determining the molar mass of Butane Gas, C4 H10 Errors

The result of this error

Improvement

Extra water left in the lighter

One of the causes to the difference in the mass of butane leading to this percent error is that the lighter may have had

Leave the lighter out to dry for a longer period of time (overnight), or dry more thoroughly with a hairdryer to

water left in it. Therefore, mass achieve a more accurate mass. could have been added leading to the difference in the molar masses. If there the mass was affected by the addition of water, the molar mass would result being lower than the actual value. When the water was left in the lighter, the mass of the gas was smaller due the to the extra water that was counted. Since the mass affected by the water was now smaller, it would result in a smaller molar mass because if the amount of moles remained the same, dividing it by the smaller mass would result in a smaller molar mass. Butane Gas spilling into surrounding water

Some of the bubbles of butane gas may have missed the graduated cylinder and went into the water instead, causing the mass of the lighter to go down when it was not accounted for in the cylinder. If some of the mass of the Butane spilled into the surrounding water, then the recorded mass would be smaller because it would not account for the lost mass. The incorrect mass, when divided by the correct number of moles would lead to an incorrect calculation of molar mass. This calculation would have been higher because the higher value for mass would have been divided by the same amount of moles, leading to a higher molar mass.

When putting the Butane gas into the graduated cylinder, use more precision with lighting the lighter. Holding the graduated cylinder steady and not fidgeting, which would keep all the butane in the cylinder and not lighting the lighter when it is not under the water would ensure the correct mass of the butane would be recorded.

Measurement Devices.

All devices used to measure, always have a small percent of error. There is also always the chance that when performing the lab, the human eye is not accurate whilst reading and recording measurements

Keep measuring devices on a flat surface and always read them at eye-level. Have another group member check all recordings....