Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download key sample questions test 1
Transcript
Chem 209 Review questions for test 1 a. Moles of solute per liter of solution is the definition of mole fraction molality molarity parts per million b. Which one of the following does NOT usually increase with temperature? osmotic pressure solubility of a gas in water vapor pressure solubility of a salt in water c. Which one of the following forces is most important for the solubility of octane in hexane? hydrogen bonding ion-dipole forces dipole-dipole forces London forces d. If an aqueous solution has a boiling point of 101.00 oC at 1 atm, what is its freezing point? ( for water Kf = 1.86 oC m, Kb = 0.512 oC m) 1.86 oC 3.63 oC - 1.86 oC - 3.63 oC e. Which one of the following is most likely to be soluble in a nonpolar solvent? H2O CH3OH KCl Cl2 f. Which one of the following is likely to be most soluble in H2O? CH3CH2CH2OH I2 CH3OH CH3CH2CH3 g. Which one of the following will always DECREASE the amount of O2 dissolved in water? increasing the temperature and increasing the pressure of O2 above the water increasing the temperature and decreasing the pressure of O2 above the water decreasing the temperature and increasing the pressure of O2 above the water decreasing the temperature and decreasing the pressure of O2 above the water h. Which one of the following statements is TRUE? All salts easily dissolve in water Energy is always required to break the bonds in an ionic crystal When NaCl dissolves it breaks down into Na and Cl atoms Salts dissolve readily in CH3CH2CH2CH2CH2CH3 i. A colligative property is a property of a solvent that depends on the molecular weight of the solvent, depends on the amount of solute depends on the total mass of the solvent depends on the volume of the solution j. If two salt solutions are separated by a semipermeable membrane there will be a net flow of solvent from the low concentration solution to the high concentration solution solute from the high concentration solution to the low concentration solution solvent from the high concentration solution to the low concentration solution solute from the low concentration solution to the high concentration solution k. The vapor pressure of a liquid decreases when temperature increases a nonvolatile solute is dissolved the pressure above the solution is lowered the liquid is transferred to a smaller container 1 Chem 209 Review questions for test 1 l. A solution is made by mixing one mole of toluene with one mole of benzene at 25 C. For pure benzene the vapor pressure is 80 torr and for pure toluene the vapor pressure is 50 torr. The mole fraction of toluene in the vapor above the solution is greater than 0.5 equal to 0.5 less than 0.5 m. Which one of following aqueous solutions will have the lowest freezing point 0.25 m KCl 0.2 m MgCl2 0.1 m CoCl3 0.5 m NaCl n. Which one of the following forces is most important for the high solubility of KCl in water hydrogen bonding London forces dipole-dipole forces ion-dipole forces o. The solubility of a gas is water is highest for which conditions of temperature and pressure? high P, high T low P, high T low P, low T high P, low T p. Which one of the following is NOT a colligative property? freezing point depression temperature osmotic pressure vapor pressure lowering q. Which one of the following combinations would NOT be likely form a solution ionic solid and non-polar liquid ionic solid and polar liquid polar solid and polar liquid non-polar solid and non-polar liquid r. Blood cells have a semipermeable membrane and their fluid contains dissolved ions. When blood cells are placed in a concentrated salt solution they shrink because ions pass through the cell membrane by osmosis water passes through the cell membrane by osmosis water passes through the cell membrane by reverse osmosis salt passes through the cell membrane by osmosis s. Which one of the following is a colloid that has a solid suspended in a liquid? emulsion foam sol t. aerosol A soap molecule contains a polar group at the end of a long polar chain a nonpolar group at the end of a long polar chain a nonpolar group at the end of a long nonpolar chain a polar group at the end of a long nonpolar chain . Which one of the following statements is TRUE? A mixture of liquids is always a solution A colloid is a solution A solution may have more than one phase Air is an example of a solution ____________________________________________________________ Circle the member of each of the following pairs that is likely to be more soluble in the indicated solvent. CH3CH2CH2OH or Br2 CH3CH2CH2CH2CH2OH or CH3OH CH3OH or I2 2 Review questions for test 1 Chem 209 in water in hexane _____________________________________________ in ethanol When 8.0 g of an unknown compound is dissolved in 500.0 g of carbon tetrachloride, CCl4, the freezing point of the solution is -30.7 °C. The freezing point of pure carbon tetrachloride is -22.3 °C. (Kf = 29.8 C kg mol-1 for CCl4) a. Find the molality of the solution. Tf = mKf Tf = -22.3 K - (-30.7 C) = 8.4 C m Tf 8.4 K 0.282 mole kg1 o 1 Kf 29.8 C kg mole b. Find the molecular weight of the unknown compound. 8.0 gunk 1000 gCCl4 500.0 gCCl4 0.282 molunk g 56.7 mol ________________________________________________________ The vapor pressure of pure water at 25 C is 23.8 mm Hg. What is the vapor pressure of a solution made by adding 35 g of urea to pure water. Urea is a nonvolatile, nonelectrolyte that has a molecular weight of 60 g/mol. a. Find the vapor pressure of the solution at 25 C. nurea 35 g 0.583 mol 60 g mol 1 x H 2O nH2O 200 g 11.1mol 18 g mol 1 11.1mol 0.949 11.1mol 0.583 mol PH2O x H2OPH02O 0.94923.8 mm Hg 22.6 mm Hg b. Assuming that the volume of 200 g of water is 200 mL, find the osmotic pressure in torr of this solution at 30 C. MRT 0.583 mol mol M 2.915 0.200 L L mol 1 1 2.915 0.0821L atm K mol 303 K 71.8 atm L __________________________________________________________ 2. The boiling point of pure benzene is 80.16C. A solution of 2.15 g of a solid dissolved in 20 g. of benzene boils at 81.10 C. Kb for benzene is 2.53 C/m. Assume that the solution is a nonelectrolyte. a. Find the molality of the solution. Tb = mKb Tb = 81.10 C – 80.16 C = 0.94 C m Tb 0.94 o C 0.372 mole kg1 o 1 Kb 2.53 C kg mole 3 Review questions for test 1 Chem 209 b. Find the molecular weight of the unknown compound. 2.15 gunk 20 gCCl4 1000 gCCl4 0.372 molunk g 289 mol _________________________________________________ 3 A solution is made by adding 10.0 g of NaCl (FW = 58.4 g mol to 100.0 g of H2O (MW = 18.0 g mol). The vapor pressure of pure H2O is 18 torr at 20 C. a. Find the vapor pressure of the solution at 20 C. nNaCl 10.0 g 0.172 mol 58.4 g mol 1 x H 2O nH2O 100 g 5.51mol 18 g mol 1 5.51mol 0.970 5.51mol 0..172 mol PH2O x H2OPH02O 0.97018.0 mm Hg 17.5 mm Hg b. Find the freezing point of this solution. (Kf = 1.86 C/m for water) 0.172 mol mol 1.72 1.72 m 0.100 kg kg Tf iK f m 2 1.86 o C m1 1.72 m 6.40o C molality freezing point = 0 – Tf = -6.40 oC __________________________________________________________ Calculate the osmotic pressure in torr for a 650 mL of an aqueous solution containing 42.0 g of sucrose. Assume the temperature is 25 C. (MW = 342 g/mol for sucrose) 42.0 g 0.123 mol 342 g mol 1 0.123 mol mol M 0.189 0.650 L L mol 1 1 MRT 0.189 0.0821L atm K mol 298 K 4.63atm L __________________________________________________________________________ 7 (10) Find the osmotic pressure in torr for a solution made by adding 20.0 g of NaCl (FW 58.44) to 200 mL of water. Assume the temperature is 20oC. 20.0 g 1 n 58.44 g mol 0.342 mol mol M 0.171 V 200 mL 0.200 L L = iMRT 4 Chem 209 Review questions for test 1 mol 0.0821L atm 2 0.171 293 K 82.4 atm L mol K 82.4 atm 760 torr 6.26 10 4 torr atm ___________________________________________________________________________ Assume that the partial pressure of O2 above a solution is 150 mm Hg and the partial pressure of N2 is 610 mm Hg. For water at 20 oC, the Henry’s law constant for O2 is 1.43 x10-3 mol L-1 atm and for N2 is 7.34x10-4 mol L-1 atm What is the molarity of O2 in solution? What is the mole fraction of O2 in solution? Assume that the density of water is 1.00 g/mL. FW O2 = 18 g/mol, FW H2O = 18 g/mol. Is there more N2 or O2 dissolved in the water? Show calculations to demonstrate your conclusion. ___________________________________________________________________________ a. Which one of the following DOES NOT have cis and trans isomers? 2,3-dichloro-2-butene 1,1-dichloro-1-butene 2-chloro-2-butene 1,2-dichloro-propene b Which one of the following molecules could be used to make a chain growth (addition) polymer? methanol methyl ethyl ether ethane propene c. Which one of the followings statements is FALSE? Proteins are made up from amino acids linked together by condensation reactions The genetic code is stored in the sequence of the bases in DNA The -helix is an important structure for proteins A nucleotide contains phosphate group, an ether and an organic base d. Which one of the following compounds is a saturated hydrocarbon? 4-Pentene 2-butyne 3-methyl 2-pentene e. How many isomers are there for the formula C2H2Cl2 1 2 2-methylpropane 3 4 f. Which one of the following is a polysaccharide that is used to store energy in the human body fructose glucose cellulose starch g. Which one of the following is not part of DNA? phosphate base sugar h. Which one of the bonds in the DNA double helix structure are the weakest the bonds between the bases 5 amino acid Review questions for test 1 Chem 209 the bonds between the phosphate and sugar the bond between the sugar and the base the bond between the base and phosphate i. How many isomers are there for the formula C3H6Br2 ? 2 3 5 4 j. One of the products of a condensation reaction is always an ether a protein an acid water k. Which one of the following statements is TRUE? benzene is an alkene cyclohexane is an saturated hydrocarbon alkynes sometimes have cis-trans isomers alcohols act as bases l. How many different alcohols have four carbons? Do not consider compounds with double bonds or rings 1 2 3 4 m. Which one of the following formulas most likely corresponds to a carbohydrate? C18H38O2 C6H12OH C6H12 C6H12O6 Which one of the following is an aromatic compound methyl alcohol methyl amine 2 –methylpropene methyl benzene __________________________________________________________ Draw the products of the following reactions a) trans-2-pentene and Br2 Br H H3C C C CH2 CH3 + Br2 H3C CH CH CH2 CH3 b) the reaction H between propanoic acid (CH3CH2COOH) and methanolBr O O H3C OH + HO C CH2 CH3 H3C O C CH2 CH3 + H2O c) show a reaction between the two amino acids shown below to form a peptide bond. H O C H2N NH2 C H OH + O CH CH3 OH C O H O CH3 C C N C C NH2 + H2O HO H H __________________________________________________________ 6 H Review questions for test 1 Chem 209 Draw the structures for molecules with the formula C5H10. Name all compounds. (1 point per correct structure, 1 point per correct name) __________________________________________________________ Draw the structures of the following. OH H3C H3C C CH2CH2CH2 CH3 CH CH2 CH3 3-pentanol O H3C CH2 CH3 C CH3 CH CH2 CH3 CH2 CH 2,6-dimethyl-3-heptene CH3 CH C H3C 2-hexanone CH3 C H O CH2 H3C CH3 CH2 CH 7 CH3 CH3 Review questions for test 1 Chem 209 3-methyl butanal 2,2,4-trimethylpentane 10. (5 pts) Identify the class (alcohol, alkane, alkene, alkyne, amine, amide, amino acid, aldehyde, aromatic, carboxylic acid, ether, ester, ketone) that best describes the following molecules. R and R’ are hydrocarbon groups alcohol amine aldehyde acid ketone Identify each of the four following structures as (amino acid, alkane, alkyne, alkene, aromatic, carbohydrate, dipeptide, dissacharide, nucleotide, tripeptide) nucleotide carbohydrate dipeptide amino acid Consider the molecule shown below. Use asterisks to indicate the chiral carbons. H CH3 O H H O H N C C N C * C N H CH3 OH O * C H OH 8 C OH Review questions for test 1 Chem 209 Draw the structures for four compounds with the formula C4H8. Name all compounds. (1 point per correct structure, 1 point per correct name, 8 points max) H3C H H C C C H H C H3C CH3 CH3 trans-2-butene cis-2-butene H H2C CH2 H2C CH2 CH3 C H C CH3 2-methylpropene cyclobutane 6. (10) Draw the structures for five pentenes with the formula C6H12. Name all compounds. (1 point per correct structure, 1 point per correct name, 10 points max) 2-methyl-1-pentene 2-methyl-2-pentene 3-methyl-1-pentene 4-methyl-1-pentene trans-3-methyl-2-pentene cis-3-methyl-2-pentene cis-3-methyl-2-pentene cis-3-methyl-2-pentene 9
