UNIVERSAL GAS CONSTANT (R)

Purpose: Use butane gas, C4H10, collected over water to calculate the universal gas constant, R.

Safety: Goggles. Do NOT ignite butane by flipping the flint wheel on the lighter.

PROCEDURE: 1)Submerge lighter in water, remove, shake off excess H2O, dry, record mass.

2)Fill 100ml graduated cylinder to brim w/H2O. Carefully cover opening and invert in sink filled w/H2O. Keep opening under H2O. Repeat if there are any air bubbles. 3)Hold lighter under opening of cylinder and release butane, C4H10, by depressing lever. Collect ≈95mL C4H10. Don’t allow any C4H10 bubbles to escape. Remove lighter, shake off excess H2O, dry, record mass. 4)Allow C4H10 to reach room temperature (5 minutes) then record temp. of H2O (nearest 0.1°C). 5)While maintaining equal H2O levels inside and out of cylinder, record volume of C4H10 to nearest 0.1 mL. 6)Use table below to record vapor pressure of H2O for H2O temperature.

T (°C) / 20.0 / 20.4 / 20.8 / 21.2 / 21.6 / 22.0 / 22.2 / 22.4 / 22.6 / 22.8 / 23.0 / 23.4 / 23.8 / 24.2 / 24.6 / 25.0
Pwater(torr) / 17.5 / 18.0 / 18.4 / 18.9 / 19.3 / 19.8 / 20.1 / 20.3 / 20.5 / 20.8 / 21.1 / 21.6 / 22.1 / 22.6 / 23.2 / 23.7

Data: Include units, Include units, Include units, Include units, Include units

initial mass of lighter: 14.58g / final mass of lighter: 14.35g
Temperature:Water/butane: 21.2⁰C / Pair:atmospheric pressure: 761mmHg
Volume of butane: 95mL / Pwater: water pressure:

Calculations: Show ALL Work. Include units. Keep 4 sig figs until solving for R.

1)  P-Convert Pair to atm.

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Convert Pwater to atm.

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Calculate pressure of butane (C4H10). Dalton’s Law (Pair= Pbutane+Pwater)______

2)  V-Convert volume C4H10(mL) to L.

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3)  n-Moles C4H10. Calculate mass of butane, C4H10. ______

Use mass C4H10 to calculate moles butane

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4)  T-Convert °C to K ______

5)  R-Use ideal gas law, PV=nRT, to calculate value of universal gas constant. (3 sig figs)

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6)  Calculate percent error of R. Theoretical value for R=0.0821(L·atm)/(mol·K).

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7)  Was your experimental R value too high or too low? ______

List possible sources of error. ______