I have the data, I only need the calculations of the last page. CHEM 1111Molar Mass of ButaneCautionsButane is toxic and flammable. No OPEN Flames should be used in this experiment.IntroductionWhen a new substance is prepared in the laboratory, its identity must be determined. Knowing the molar mass ofthe substance limits the list of possible identities. To determine the molar mass, two pieces of information must be known;the mass of the sample and the number of moles of substance present in that particular mass. For any sample,determining its mass is straightforward – place a quantity on or in a container on the balance, and read the mass itdisplays. Determining the number of moles is not as straightforward. In the case of a gaseous sample, knowing itspressure and volume at a specific temperature provides enough information to determine the number of moles present.Using the mass and number of moles, the molar mass can be determined.One method of determining the volume of a gas sample at a known pressure is to collect it over water using asetup similar to one found in most general chemistry textbooks. If the volume (V), temperature (T) and total pressure(Pgas) of the collected gas are measured, the gas law constant (R) and the ideal gas law can be used to determine themoles (ngas) of hydrogen produced by the sample:PgasV nngasRT(Equation 1)Determining the pressure of collected gas is not as straightforward as simply measuring atmospheric pressure. Samplesof liquid water in any container always have a small amount of water vapor present just above the surface (vaporpressure), which must be accounted for. Accounting for this small quantity of water vapor requires using Dalton's law ofpartial pressures:Protal PgasPH,0(Equation 2)Since the gaseous sample is collected over water in an enclosed flask, one can assume the gas is saturated with watervapor at barometric pressure. Thus, the total pressure observed under these conditions is equal to the sum of the vaporpressure of water at that temperature and the pressure of the gas from the experiment. The vapor pressure of water isconstant at various temperatures and here again, can usually be found in most generalVapor Pressure of Waterchemistry textbooks.Temp (°C)VP (torr)1613.6Butane is a gas at normal room conditions, however in disposable lighters it is a1714.5liquid. This phase change is achieved by putting a sample of butane under high pressure1815.5within the lighter. When the valve of the lighter is depressed it provides an opening,1916.5depressurizing the container and allowing the liquid butane to escape in the form of a2017.5gas. Butane is a hydrocarbon, composed of only carbon and hydrogen atoms connected2118.6by covalent bonds. The composition of butane leads to its physical and chemical2219.8properties; butane molecules do not interact significantly with each other or with other2321.0molecules. Hence, butane is a gas at room temperature and does not dissolve2422.42523.7significantly in water. These properties make butane an ideal sample for this particular2625.2experiment.2726.7In this experiment you will collect a butane gas sample in a container by the2828.3water displacement method, allowing direct measurement of the volume of butane gas2930.0collected. The pressure of the butane gas can be determined using Equation 2 above,3031.8Page 1 of 3 CHEM 1111Molar Mass of ButaneData SheetThese tables and all work for calculations are to be included in the laboratory notebook.UNITSTRIAL 1TRIAL 2TRIAL 3Final Mass of Lighter16.13415.32115.142Initial Mass of Lighter16.30415.90715.321Mass of Butane0.170.5860.179Volume of Gas81.580.5mL 80.5CollectedAir TemperatureKelvins295.15Water Temperature22.0Vapor Pressure of H20Barometric Pressurecm74.8Calculations1. Use Equation 2 to determine the partial pressure of butane in the graduated cylinder for each trial.2. Use the ideal gas law to determine the moles of butane collected for each trial.3.Determine the molar mass of butane for each trial.4.Calculate a percent error in experimentally determined molar mass of butane.Page 3 of 3

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