Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
South Pasadena • AP Chemistry Name 10 ▪ States of Matter Period 10.3 1. The diagrams show the results of paper chromatography of four separate amino acids in two different solvents. Date PROBLEMS – MIXTURES 2. In an experiment, a mixture of amino acids was separated using paper chromatography and solvent Y. The resulting paper is shown below. (a) Use the table of Rf values below to decide which of the labelled spots, P, Q or R is arginine. Amino Acid Rf in Solvent X Rf in Solvent Y Alanine Arginine Glutamic Acid Glycine Tyrosine Leucine Proline 0.70 0.72 0.38 0.50 0.66 0.91 0.95 0.38 0.20 0.30 0.26 0.45 0.73 0.43 (a) Calculate the Rf value for amino acid B in (i) Solvent A and (ii) Solvent B. (b) Explain the difference in Rf value. (b) In a separate experiment a mixture of alanine, arginine and tyrosine was applied and solvent X moved 20 cm up the paper. How far up the paper from the origin would Tyrosine be located? (c) What is the correct order of the following steps to describe the process of 2-way chromatography? (number from 1-8) Calculate Rf values. Run the chromatogram in the 1st solvent Measure the distance the spots and solvent have moved Apply mixture to the chromatography paper Spray with locating agent Run the chromatogram in the 2nd solvent Rotate the paper Mark the paper The diagram shows the result of a two-way chromatogram. 3. What is the vapor pressure of a solution by mixing 35.0 grams of urea (CH4N2O) with 150.0 grams of acetone (C3H6O) at 40°C? Assume urea is nonvolatile, and the vapor pressure of pure acetone is 400. torr at 40°C. 4. A sample of magnesium nitrate is added to 500 g water. (a) What mass of magnesium nitrate is required to lower the freezing point of water to −12°C? (b) What is the boiling point temperature of water for this solution? (d) Which letters correspond to amino acids that are equally soluble in the first solvent that was used? (e) Explain how you can tell that Q and R are not the same amino acid. 5. Which of the following solutions would you expect to have the lowest freezing point? (The molality, m, mol solute is the kg solvent ratio. a. 0.010 m NaCl d. 0.050 m glycerol b. 0.100 m sugar e. 0.060 m Ca(NO3)2 c. 0.070 m KNO3 f. 0.075 m KCl 6. Consider a solution with 64 g of methanol 7. 0.64 g of adrenaline in 36.0 g of carbon (CH3OH) and 69 g of ethanol (C2H5OH). tetrachloride produces a boiling point elevation of Methanol: MM = 32.04 g/mol, Pvap = 90 torr 0.49°C. What is adrenaline's molar mass? (kb Ethanol: MM = 46.07 g/mol, Pvap = 45 torr carbon tetrachloride = 5.03 °C·kg·mol–1) (a) What is the total vapor pressure of the solution? (The total vapor pressure is the sum of the vapor pressures of each component in the solution.) (b) What IMFs are involved in the substances? Which has stronger intermolecular forces? Why? AP Chemistry 1993 #2 Elemental analysis of an unknown pure substance indicates that the percent composition by mass is as follows: Carbon - 49.02% Hydrogen - 2.743% Chlorine - 48.23% A solution that is prepared by dissolving 3.150 grams of the substance in 25.00 grams of benzene, C6H6, has a freezing point of 1.12°C. (The normal freezing point of benzene is 5.50°C and the molal freezing-point depression constant, kf, for benzene is 5.12 C°/molal.) (a) Determine the empirical formula of the unknown substance. (b) Using the data gathered from the freezing point depression method, calculate the molar mass of the unknown substance. (c) Calculate the mole fraction of benzene in the solution described above. (d) The vapor pressure of pure benzene at 35°C is 150. mmHg. Calculate the vapor pressure of benzene over the solution described above at 35°C.