CHEM 2800 Lecture Notes - Lecture 2: Ethyl Acetate, Phase Boundary, Chemical Equilibrium

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2 Dec 2017

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Title: experiment #1 - vapor pressure of a liquid. The objective of this experiment is to find the heat of vaporization, also called enthalpy of vaporization, by obtaining the vapor pressure of ethyl acetate as a function of its temperature. Vapor pressure is an extremely important physical property of a chemical compound. Chemical compounds with a low molecular weight have high vapor pressures, above one atmosphere, at normal temperatures in the environment. On the other hand, chemical compounds with a high molecular weight have low vapor pressures. The vapor pressure of a liquid can be measured when the liquid is in equilibrium with its vapor at a certain temperature using a manometer. The relationship between the vapor pressure of a certain liquid as a function of its temperature is described by the clausius-clapeyron equation. Thermal, mechanical, and chemical equilibrium must exist when two phases, such as liquid and vapor, are in equilibrium.

Related Questions

Need 69,74,75,77

Please give me Post lab questions 2 and 3 at the bottom.

Experiment 7 - Molar Mass of a Volatile Liquid

Introduction. Given the mass of vapor at conditions of known pressure, volume, and temperature, one can determine the molar mass of the vapor. The Ideal Gas Law mathematically relates the quantities of pressure (P in atm), volume (V in liters), and temperature (T in Kelvin) and the quantity of gas (n in moles). Using the expression PV=nRT where R equals the Ideal Gas Constant 0.0821 L*atm/K*mol, one can determine the quantity of gas under given conditions of pressure, volume and temperature. The number of moles of gas is found by

n =

Because the molar mass (MM) is defined as the mass of one mole of substance in units of g/mol, the molar mass of the vapor can be determined by

MM= mass of vapor in grams/moles of vapor

In this experiment, an unknown volatile liquid is heated in a boiling water bath and is vaporized. The vapor forces air from the flask until the pressure within the flask equals the barometric pressure of the lab. As with all gases, the vapor occupies the entire volume of its container. The temperature of the vapor equals the temperature of the boiling water bath. After 8-10 minutes, the vapor is cooled. The mass of the condensed liquid is determined and the molar mass is calculated as described above.

Notes:

Check out unknown from stockroom

Record unknown number

Before weighing your condensed vapor, thoroughly dry the outside of the flask and make sure that no water is trapped under the foil cover

Do not rinse your flask with water between trials

Dispose of waste in appropriate container

Procedure. You will record your data and calculations in your lab notebook.

Obtain an unknown liquid and a 3 inch aluminum foil square. You will need two 600 or 800 mL beakers, and 3 or 4 boiling chips.

Add 3 or 4 boiling chips to the water in an 800 mL beaker and heat the water to the boiling point. Continue heating for 8 to 10 minutes after the water comes to a rolling boil. The temperature of the boiling water is 100.0^oC. This will be the temperature of the vapor. Convert the temperature to Kelvin and record in your lab notebook.

800 mL Beaker

250 mL Flask

11.

Chemical Molar Mass

1-chlorobutane 92.6 g/mol

t-butyl chloride 92.5 g/mol

trichloroethylene 131 g/mol

2-propanol 60.1 g/mol

Ethyl acetate 88.1 g/mol

n-hexane 86.2 g/mol

cyclohexane 84.2 g/mol

2-butanone 72.1 g/mol

Post Lab Questions: Answer the following questions using complete sentences. Include them after your conclusion.

1. If a lab group did not keep the flask submerged in boiling water for a full ten minutes, and some unknown never vaporized, how would that affect the calculated molar mass? In other words, would it make the calculated value too high or too low? Explain why.

2. While performing this experiment, ten lab groups have ten different unknown volatile liquids with a range of molar masses. If all lab groups have exactly the same size of flask (255 mL), and all groups took their unknown vapor to the same temperature (100.0^oC) and pressure (760.0 mmHg), how would the number of molecules within the different flasks compare? Would it vary with molar mass? How? Explain.

3. A student has determined that an unknown liquid is either 1-chlorobutane or t-butyl chloride. What other physical property(s) could be used to determine the identity of the unknown?

An instrument used to measure the pressure of a gas in a laboratory is called a barometer manometer sphygmomanometer spectrophotometer spectrometer The pressure of a gas in a container is1.85 atm and occupies a volume of 12.5 L If the original volume is reduced by hall at constant temperature, what would happen to the pressure? The pressure would ... double reduce by half remain the same On a hot summer day, you notice that a bag of chips left in your vehicle has inflated. As temperature increased, gas molecules .......... kinetic energy and the volume of gas inside the bag ....... Lost/increased gained/decreased lost/decreased gained/increased What mass of oxygen gas (O_2) is needed to fill a 585 L tank at STP? 0 835 kg 0.765 kg 0.417 kg Which of the following will cause the volume of an ideal gas to triple in value Raising the temperature from 25 degree C to 75 degree C at constant pressure. Lowering the absolute temperature by a factor of 3 at constant pressure. Lowering the pressure by a factor of 3 white the temperature stays constant. A 0.334 g sample of an unknown halogen occupies 109 mL at 398 K and 1.41 atm. What is the identity of the halogen? Br_2 F_2 C1_2 l_2 Define vapor pressure. partial pressure cf water in a Squid mixture partial pressure of wafer in a gases mixture condensation of water A mixture of 1.0 mol He and 1.0 mol No are at STP in a rigid container. Which of the following statements is TRUE Both gases have the same average kinetic energy. Both gases contribute equally to the density of the mixture under these conditions. Both gases have the same molecular speed. The following reaction is used to generate hydrogen gas in the laboratory Mg(s) + 2 HC1(aq) rightarrow MgC1_2(aq) + H_2(g) If 243 mL of gas is collected at 25 degree C and has a total pressure of 745 mm Hg. what mass of hydrogen is produced? Listed are vapor pressures at select temperatures: Listed are water vapor Pressures at select temperatures: 0.0144 g H_2 0.0717 g H_2 0.0190 g H_2 Which of the following compounds will behave LEAST like an ideal gas at low temperatures? He SO_2 H_2 N_2 F_2 A container Filed with neon and argon gas is 25.00% by volume neon. What is the partial pressure of argon it the total pressure inside the container is 5 500 atm? 412 5 atm 1.375 atm 4.125atm 28 5 L of an unknown gas has a mass of 55.92 g at STP. What is the identity of the unknown gas? CO_2 O_2 N_2 Explain what would happen to the following equilibrium upon the addition of more hydrogen gas? H_2O(g) + CO(g) doubleheadarrow H_2(g) + CO_2(g) producing more reactants producing more CO_2 equilibrium will not be attected For the following reaction, K_5 = 5.6 x 10^-6 (at 400 K): 2 NOC(g) doubleheadarrow 2 No_2(g) + C1_2(g) If [NOCI] = 0.0222 M, [CI_2] = 0.0222 M, [NO_2] = 0.989 M at once, which statement would be true? The rate of forward and reverse reaction are equal. Neither forward nor reverse reaction would occur. Rate of forward reaction would be taster. Rate of reverse reaction would be faster. K_c = 1.10 times 10^18 for CO(g) + 1/2 O_2(g) doubleheadarrow CO_2(g) Calculate the equilibrium concstant K_0 for the following CO_2(g) doubleheadarrow CO(g) + 1/2 O_2(g) 1.04 times 10^9 0.55 times 10^18 -1.10 times 10^18 9.09 times 10^19

CHEM 2800 Lecture Notes - Lecture 2: Ethyl Acetate, Phase Boundary, Chemical Equilibrium

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