CHEM 1120 Midterm: UT Chattanooga CHEM 1120 1120exam1-fall2009

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turquoisegnu128

7 Mar 2019

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Chem 122 rybolt exam 1 fall 2009 name_________________________________ (print) Other needed information is given in the problem or written on the board or found in the periodic tables you will use during exam. For numerical problems, be sure to show your work, include units and circle your final answer. If several choices are given, circle the correct answer. Your written answers should be brief and to the point. You can use your own calculator on the exam, but no notes, books, external information, or other electronic devices are to be used. No cell phone is to be used in the exam room. 1 cal = 4. 184 j r = 0. 08206 (l atm/ mol k) or r= 8. 31j/mol k. 1 atm = 760 torr = 1. 01x105 n/m2 1 g = 6. 02x1023 amu oc=(of-32)/1. 8 k=oc+273: an aqueous solution of sodium nitrate nano3(aq) has a concentration of 0. 363 m and a density of 1. 0185 g/ml.

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How do you solve #8?

Brooklyn College of C.U.N.Y Spring 209 Chemistry 1.2 Makeup Midterm Exam Lab. Sectio Physical Constants R-0.0821 L.atrn /mM1 K: 1 atrm-760 Torr; h-6.626 x 10" Js. c-300 x 10' mis Multiple Choice Question4 points each. Circle the correct choice I. How many orbitals are there in the n - 3 shel 2. Which of the following is not a valid set of four b6 ( 4)12 e) none of the preceding choices quantum numbers to describe an electron in an atom? 3. Which pair of elements would you expect to exhibit the most similar physical and chemical peoperties? a) As and Se Na and ci As and Sb s) B and Bensnp 4) The rn unpaired electrons in the ground state of an atom of Co is... ree (C) five (D) seven (E) none of the preceding choices 0è®ä¸ä½å£ wch of the following processes is exothermic? a) lonization of a sodium atom b) Formation of gaseous Which of the following bonds is the most polar? a) N-O b)o-F ) B-o )so e)all are equally polar t what temperature (in C) will 25.0 g of carbon dioxide (at 1.00 atm) occupy 21.3 L? 8Â°C b) 461 C c) -263Â°C d)-270Â°C e) 113Â°C How many times more rapidly will hydrogen (H,) gas effuse through a pinhole than will deuterium ( Deuterium is an isotope of hydrogen with a molecular mass of 4.0 g'mole. (A) 2 (B)2 (C)2v2 (D)4 9, Which of the following arrangements from lowest to highest in first ionization energies is correct ? 10. In which of the following compounds obeys the octet rule? a) XeF b) BF, c) CIO d) SO, pone of the preceding choicees 11. The bright spectral lines observed in the emission spectrum of a flame or gas discharge tube are due to a) the absorption of light at specific wavelengths b) the formation of an excited state of atoms the transition of an atom from an excited state to a lower energy state d) the change from anti-parallel to parallel electron spins in an atom oxygen at 25 Â°C. Comparing the pressure of the hydrogen to the exygen, the ratio will be From Bond Dissociation Enthalpies: Î11D (CI-CI)-243 klinolalo (F-F )-159 kJ/mol; Î1lo (CHF)-25 12.A one-liter container is filled with one mole of hydrogen at 25 Â°C.A second one-liter container is filled with or 2CIF(R) alculate the enthalpy, AH, for the chemical reaction: Cl (g)+ F: (g) (a)-147 kJ (b)-108 kJ (c) +171 kJ (d) +912J (H lou, mory t,hes more rapidy wil, hydrogen w many tes more ro

How do you answer 1-4?

Physical Constants R-00821 L.atm rnol. K: 1 atm = 760 Torr; h-6626 x 10". Js; c-3.00 x 10e mis Multiple Choice Question-4 points each. Circle the correct choice. 1. How many orbitals are there in the n - 3 shell? )3 b)6 )9 d) 12 e) none of the preceding choices 2. Which of the following is not a valid set of four quantum numbers to describe an electron in an atom? 3. Which pair of elements would you expect to exhibit the most similar physical and chemical properties? a) As and Se b) Na and Cl c) As and Sb d) B and Be 4) The number of unpaired electrons in the ground state of an atom of Co is.. (A) one (B) three (C) five (D) seven (E) none of the preceding choices S. Which of the following processes is exothermic? a) lonization of a sodium atom b) Formation of gaseous chlorine atoms from Cl, (g) c) Breaking apart of NaC1 (s) into ions d)Addition of an electron to a chlorine atom 6. Which of the following bonds is the most polar? a) N-O b)O-F e) B-O d)S-o e) all are equally polar At what temperature (in C) will 25.0 g of carbon dioxide (at 1,00 atm) occupy 21.5 L? 188Â°C b) 461Â°C c) -263Â°C d)-270Â°C e)113Â°C How many times more rapidly will hydrogen (H2) gas effuse through a pinhole than will deuterium (D ) gas? Deuterium is an isotope of hydrogen with a molecular mass of 4.0 g/mole. (A) V2 (B) 2 (C)2v2 (D) 4 9. Which of the following arrangements from lowest to highest in first ionization energies is correct ? 10. In which of the following compounds obeys the octet rule? 1. The bright spectral lines observed in the emission spectrum of a flame or gas discharge tube are due to a) XeF b) BF, c) Cio d) so e) none of the preceding choicees a) the absorption of light at specific wavelengths b) the formation of an excited state of atoms c) the transition of an atom from an excited state to a lower energy state d) the change from anti-parallel to parallel electron spins in an atom 2. A one-liter container is filled with one mole of hydrogen at 25 Â°C. A second one-liter container is filled with one mole f oxygen at 25 Â°C. Comparing the pressure of the hydrogen to the oxygen, the ratio will be Fro n Bond Dissociation Enthalpies: AHD (CI-CI)-243 kJrnolAMD (F-F )ä¸159 klinol; lculate the enthalpy, AH, for the chemical reaction: Cl: (g)+F: (g) 2CIF(R) )-147 kJ (b)-108 kJ (c)+171 kJ (d) +912 k AHD (CI F)-255 kJ mol ;

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?

CHEM 1120 Midterm: UT Chattanooga CHEM 1120 1120exam1-fall2009

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