Chem 1711 Name ______________________________________ Quiz 5 October 21, 2014 PV = nRT 1. A sample of gas at some volume and temperature exerts a pressure of 25.64 atm. Determine what will happen when each of the following changes is made independently to this system with this starting P, V, and T. a. If, at constant volume, an additional 0.200 mol gas is added and the temperature is increased, will the pressure exerted increase, decrease, or remain constant? b. c. ______________________________ If the volume occupied by this sample of gas is increased at constant temperature, will the pressure exerted increase, decrease, or remain constant? ______________________________ If 1.50 mol of a different gas is added to the container at constant V and T, will the total pressure exerted by the system be less than, greater than, or equal to 25.64 atm? 2. R = 0.08206 L•atm•K—1•mol—1 PM = dRT ______________________________ Consider a mixture of He (g) and Ar (g) that exerts a total pressure of 4.50 atm in a 2.50 L vessel at 315 K. In this mixture the mole fraction of helium is 0.883. a Determine the total amount (in mol) of gas in this mixture. ntot = ____________________ mol b. Determine the amount (in mol) of helium in this mixture. nHe = ____________________ mol c. Determine the partial pressure (in atm) exerted by the argon in this mixture. PAr = ____________________ atm 3. a. True or False? For a sample of an ideal gas at constant T, a plot of P•V vs. V will be a curve. b. At STP, the volume occupied by 0.750 mol of an ideal gas is ________________________ L. c. A pressure of 1624 mmHg is equal to _______________________ torr. d. True or False? For a given sample of gas at constant P, density will decrease as temperature increases.____________ e. Consider a mixture of two nonreactive gases X (g) and Z (g) at a constant volume and temperature. The partial pressure of X (g) is 791 torr, and the partial pressure of Z (g) is 158 torr. For this mixture, Ptot = ______________________ torr, and χZ = _______________________ . ________________ 4. a. Calculate the volume (in L) occupied by 64.950 g Xe (g) at 495 K and 6.94 atm. _______________________ L b. Determine the molar mass of a gas with a density of 0.820 g/L at 0.722 atm and 72°C. ___________________ g/mol c. Determine the molar volume (in L/mol) of a gas at 525 mmHg and 194 K. ___________________ L/mol d. A 0.0825 mol sample of Ne (g) exerts a pressure of 0.791 atm at some T and V. If additional Ne (g) is added (at the same T and V), and the pressure exerted increases to 0.909 atm, determine the number of additional mol gas added. _____________________ mol 5. Consider the combustion of hexane: 2 C6H14 (g) + 19 O2 (g) 12 CO2 (g) + 14 H2O (g). 275 g of O2 (g) is allowed to react with excess hexane, and the reaction goes to completion. Determine the pressure (in atm) exerted in a 5.000 L vessel at 20°C by the CO2 (g) produced. _______________________ atm Bonus Questions (worth a possible maximum of 4 points added to your Quiz 4 score): 1. Pyridine (C5H5N) is a weak base. Complete the equation below to show how pyridine ionizes in water: C5H5N (aq) + H2O (l) _______________ (aq) + _______________ (aq) 2. Write the net ionic equation for the neutralization reaction between nitrous acid and potassium hydroxide: 3. A sample of Na (s) is combined with H2O (l) . Circle all of the statements below that are true. O undergoes a 2 e– reduction Na undergoes a 2 e– oxidation 4. Na is the reducing agent H is reduced O2 is the oxidizing agent in the balanced equation 1 mol H2 (g) is formed no reaction will occur Circle the letter of the one reaction below that will not occur as written. a. Ni (s) + 2 HCl (aq) NiCl2 (aq) + H2 (g) d. HIO3 (aq) + NH3 (aq) NH4IO3 (aq) b. Ni (s) + MgCl2 (aq) Mg (s) + NiCl2 (aq) e. Br2 (l) + 2 KI (aq) 2 KBr (aq) + I2 (s) c. 2 HNO3 (aq) + CaCO3 (s) Ca(NO3)2 (aq) + H2O (l) + CO2 (g) f. all of these will occur as written Chem 1711 Name ______________________________________ Quiz 5 October 21, 2014 PV = nRT 1. R = 0.08206 L•atm•K—1•mol—1 PM = dRT a. True or False? For a given sample of gas at constant P, density will decrease as temperature increases.____________ b. A pressure of 1760 torr is equal to _______________________ mmHg. c. True or False? For a sample of an ideal gas at constant T, a plot of P•V vs. V will be a curve. d. At STP, the volume occupied by 0.250 mol of an ideal gas is ________________________ L. e. Consider a mixture of two nonreactive gases X (g) and Z (g) at a constant volume and temperature. The partial pressure of X (g) is 841 torr, and the partial pressure of Z (g) is 325 torr. For this mixture, ________________ Ptot = ______________________ torr, and χZ = _______________________ . 2. Consider a mixture of He (g) and Ar (g) that exerts a total pressure of 5.75 atm in a 3.00 L vessel at 333 K. In this mixture the mole fraction of helium is 0.264. a Determine the total amount (in mol) of gas in this mixture. ntot = ____________________ mol b. Determine the amount (in mol) of helium in this mixture. nHe = ____________________ mol c. Determine the partial pressure (in atm) exerted by the argon in this mixture. PAr = ____________________ atm 3. A sample of gas at some volume and temperature exerts a pressure of 25.64 atm. Determine what will happen when each of the following changes is made independently to this system with this starting P, V, and T. a. If the volume occupied by this sample of gas is increased at constant temperature, will the pressure exerted increase, decrease, or remain constant? b. If, at constant volume, an additional 0.200 mol gas is added and the temperature is increased, will the pressure exerted increase, decrease, or remain constant? c. ______________________________ ______________________________ If 1.50 mol of a different gas is added to the container at constant V and T, will the total pressure exerted by the system be less than, greater than, or equal to 25.64 atm? ______________________________ 4. a. Calculate the volume (in L) occupied by 164.95 g Xe (g) at 495 K and 6.94 atm. _______________________ L b. A 0.0825 mol sample of Ne (g) exerts a pressure of 0.791 atm at some T and V. If additional Ne (g) is added (at the same T and V), and the pressure exerted increases to 1.909 atm, determine the number of additional mol gas added. _____________________ mol c. Determine the molar mass of a gas with a density of 1.820 g/L at 0.622 atm and 92°C. ___________________ g/mol d. Determine the molar volume (in L/mol) of a gas at 625 mmHg and 414 K. ___________________ L/mol 5. Consider the combustion of hexane: 2 C6H14 (g) + 19 O2 (g) 12 CO2 (g) + 14 H2O (g). 275 g of C6H14 (molar mass = 86.17 g/mol) is allowed to react with excess O2, and the reaction goes to completion. Determine the pressure (in atm) exerted in a 5.000 L vessel at 20°C by the CO2 (g) produced. _______________________ atm Bonus Questions (worth a possible maximum of 4 points added to your Quiz 4 score): 1. Pyridine (C5H5N) is a weak base. Complete the equation below to show how pyridine ionizes in water: C5H5N (aq) + H2O (l) _______________ (aq) + _______________ (aq) 2. Write the net ionic equation for the neutralization reaction between nitrous acid and potassium hydroxide: 3. A sample of Na (s) is combined with H2O (l) . Circle all of the statements below that are true. 4. Na undergoes a 2 e– oxidation in the balanced equation 1 mol H2 (g) is formed O undergoes a 2 e– reduction Na is the reducing agent H is reduced O2 is the oxidizing agent no reaction will occur Circle the letter of the one reaction below that will not occur as written. a. HIO3 (aq) + NH3 (aq) NH4IO3 (aq) d. Ni (s) + MgCl2 (aq) Mg (s) + NiCl2 (aq) b. Br2 (l) + 2 KI (aq) 2 KBr (aq) + I2 (s) e. Ni (s) + 2 HCl (aq) NiCl2 (aq) + H2 (g) c. 2 HNO3 (aq) + CaCO3 (s) Ca(NO3)2 (aq) + H2O (l) + CO2 (g) f. all of these will occur as written

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