Buffer Solution - General Chemistry - Solved Quiz, Exercises of Chemistry

Download Buffer Solution - General Chemistry - Solved Quiz and more Exercises Chemistry in PDF only on Docsity! 1. 10 pts. Circle T or F to indicate if the statement is True or False: F In order for an exothermic reaction to occur, the reactants must be less entropic than the products. T A buffer solution can be made by combining a weak acid and its conjugate base in roughly equal proportions. F When a solution containing a weak acid is titrated with a strong base, the pH at the equivalence point will be less than 7. T In a constant-volume (bomb) calorimeter, the heat that is given off by the reaction is equal to the difference in energy between products and reactants. T According to the second law of thermodynamics, the entropy of a chemical system can decrease only of the entropy in the surroundings increases by a greater amount. 2. 20 pts. Place your answers with units in the box to the left of each question. Use the correct number of significant figures. You will find scratch area and constants on the last page of this exam. -15 kJ For a chemical process that gives off a gas, we observe that 35 kJ of heat is taken from the environment into the reaction vessel while 50 kJ of work is done by the expanding gas. What is the change in energy for the reaction (sign included)? 4.55 What is the pH of a buffer solution that is 0.100 M weak acid and 0.120 M in its conjugate base? The Ka of the weak acid is 3.4 x 10-5. products In the following reaction, ( ) ( )( ) aq aqsAgCl Ag Cl + −→ + , which is more entropic, the reactants or the products? .00013 The solubility-product constant for PbSO4 is 1.6x10-8. How many moles of lead (II) sulfate will dissolve in 1.0 L of solution? +2.89 kJ Using the table provided with the exam, compute the free energy change (∆G) for the following reaction at a temperature of 298 K: 4 2 4 2( ) 2 ( ) ( ) 2 ( )CCl g H g CH g Cl g+ → + Docsity.com 3. 5 pts. The heat capacity of a certain liquid is 0.317 J/g-K. If a 15.0 gram sample of this liquid at 25.0 °C is subjected to 1.50 kJ of heat, what will be the final temperature of the sample? o 1500 315 (.317)(15) 25 315 340 final q T C mass T C ∆ = = = × = + = 4. 5 pts. What is the pH of a solution prepared by mixing 65.0 mL of a 0.1920 M NaOH with 35.0 mL of a 0.4500 M acetic acid solution (HAc)? 6 5 15.75 12.48 12.48[ ] .0327 [ ] .1248 100 100 4.585 10(.1248 )1.75 10 (.0327 ) 5.34 HA M A M xx x x pH − − − = = − = = = ×+ × = − = 5. 10 pts. A student uses a buret to transfer 20.00 mL of a 0.1000 M HCl solution to a 100.0 mL volumetric flask. Then she adds to this 20.00 mL of a 0.1000 M diethylamine solution. Finally she uses water to fill to the mark. What is the concentration of all ions in the resulting solution? What is the pH of the resulting solution? Be sure to answer both of these questions for full credit. This is the equivalence point of a strong acid – weak base titration. Treat this as a weak acid problem with the conjugate acid as the weak acid. You need to use the Ka for the conjugate acid. 3 714 2 11 4 2[ ] .0200 100 [ ][ ] [ ] 4.82 101.0 10 1.16 10 8.6 10 .02 6.32 a BH M H O B K BH xx x pH + + + −− − − = = = = ×× = × = × − = Docsity.com