Practice problems for test 1 PDF

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Practice question for exam 1.
Chem 1312...

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Practice problems for Test 1 1. How much heat is required to evaporate 560 g of ethanol if the heat of vaporization (delta H vap ethanol) = 38.7 kJ/mol? 2. How much heat is required to convert 76.4 g of liquid acetone (MW = 58.08 g/mol) at -30 C to a solid at – 115 C?

3. Determine the heat of vaporization for a compound with a vapor pressure of 24.3 torr at 273 K and 135 torr at 325 K. 4. The molar enthalpy of vaporization of hexane is 28.9 kJ/mol and the boiling point is 68.73 C. What is the vapor pressure of hexane at 25 C?

5. Calculate the vapor pressure of benzene at 25.5 C if the boiling point of benzene = 80.1 C and the molar heat of vaporization = 30.8 kJ/mol. 6. Oxygen has k = 1.26 x10-3 M/atm. If the molar fraction of oxygen in air is 0.21 atm, what is the molar solubility of oxygen in an aquarium at P = 1.00 atm?

7. A solution is made by mixing 100.0 g water and 100 g ethanol (C2H5OH. Calculate the mol fraction of each substance. 8. Calculate the molality of 25.0 g of KBr dissolved in 750 mL of water.

9. Determine the concentration of a solution that contains 825 mg Na2HPO4 dissolved in 450 mL of water in: a. Molarity b. Molality c. Mol fraction 10. Calculate the boiling point of sea water (kb = 0.512 C/m). 11. Calculate the boiling point of a solution that contains 1.5 mol NaI dissolved in 1.25 kg of water (kb = 0.512 C/m).

12. Calculate the freezing point of a solution composed of 23.4 g of CaF2 dissolved in 175 g water (kf = - 1.86 L kg/mol).

13. Calculate the molality of an aqueous ionic solution XY with a boiling point of 105.0 C (kb = 0.512 C/m).

14. How much glucose C6H12O6 (MW 180g/mol) per liter should be used for an IV solution to match the 7.65 atm at 37 C osmotic pressure of blood? 15. One mol of table salt is dissolved in 1 L of water at 27 C. What would be the osmotic pressure of the solution?

16. The osmotic pressure of KCl at 300 K is 50 atm. What is the molar concentration of KCl in this solution? 17. Write the rate law for the following reactions: a. 2 H2O2 (aq) --------- 2 H2O (l) + O2 b. 2 NO (g) + O2 (g) ----------- 2 NO2 (g) 18. The average rate of disappearance of ozone in the reaction 2 O3 (g) --------- 3 O2 (g) is found to be 8.9 x10-3 atm over a certain interval of time. What is the rate of appearance of O 2 during this interval? 19. The rate constant k is dependent on: a. The concentration of the reactant b. The concentration of the product c. The temperature d. The order of the reaction e. None of these 20. The rate expression for a particular reaction is: Rate = k[A][B] 2. If the initial concentration f B is increased from 0.1 M to 0.3 M, the initial rate will increase by which of the following factors? a. 3 b. 27 c. 4 d. 6 e. 9 21. A general reaction written as 2A + 2B ------- C + 2D yields the following data: [A]

[B]

initial rate

0.100 M

0.100 M

4.00 x10-5 mol/Ls

0.200 M

0.100 M

4.00 x10-5 mol/Ls

0.100 M

0.200 M

8.00 x10-5 mol/Ls

What is the order of reaction with respect to A and B? What is the overall order of the reaction? What is the numerical value of the rate constant?

22. For which order reaction is the half life of the reaction independent of the initial concentration of the reactants? a. Zero order b. First order c. Second order d. All of these e. None of these 23. If the reaction 2 HI -------- H2 + I2 is second order, which of the following will yield a linear plot? a. Log[HI] vs time b. 1/[HI] vs time c. [HI] vs time d. ln [HI] vs time 24. Calculate the activation energy (Ea) for a reaction when the temperature increases from 317 K to 427 K. (R = 8.314 J/mol K) 25. What phase change is an exothermic process? a. Freezing b. Melting c. Evaporation 26. What predominant intermolecular force is in HCl? a. Dipole-dipole b. Hydrogen bonding c. London forces 27. What predominant intermolecular force is in NH3? a. Dipole-dipole b. Hydrogen bonding c. London forces 28. Which liquid has the lowest vapor pressure based on the principles of intermolecular forces? a. Water b. Ethanol (CH3CH2OH) c. Ethyl ether (CH3CH2OCH2CH3) 29. Which molecules are soluble in water?

a. Glucose, methanol, ethanol b. Carbon dioxide, methane, methanol c. Glucose, hexane, ethanol 30. Which would be a strong electrolyte in solution? a. PbI2 b. KCl c. Al(OH)3 31. Which of the following would be a poor choice for making a conductive solution? a. C6H12O6, CH3OH, CH3CH2OH b. HCl, KBr, HNO3 c. NaOH, KOH, LiOH 32. At what temperature does salt water freeze? a. 0 C b. Below 0 C c. Above 0 C 33. What would be the best method for lowering the freezing point of water in an ice tray that is in the freezer? a. Decrease the temperature of the freezer b. Decrease the temperature of the freezer and increase the surface area by transferring the water to a larger ice tray c. Add some table salt to the water 34. What happens to the freezing point of water when ethylene glycol is added? (ethylene glycol is a non electrolyte) a. No effect on the freezing point b. Increasing the freezing point c. Decreasing the freezing point 35. Patients who enter the emergency room dehydrated are usually given a sterile saline solution intravenously. The solution is isotonic to prevent cell damage. What would happen if the solution was hypotonic? a. Hypotonic solutions have a higher osmotic pressure than that within cells so hemolysis can occur b. Hypotonic solutions have a lower osmotic pressure than that within cells so hemolysis can occur c. Hypotonic solutions have the same osmotic pressure as that within cells so hemolysis can occur...