31 Calculate The Cu Zn Ratio At Which The Following Reaction Is Spontaneous At 25 C Hint To Be Spontaneous The 1 (101.71 KiB) Viewed 12 times
31. Calculate the [Cu]/[Zn² ] ratio at which the following reaction is spontaneous at 25°C. Hint: to be spontaneous the Ecell must be positive, or higher than zero. Cu(s) + Zn²+ (aq) → Cu² (aq) + Zn(s) 32. Calculate the voltage for each of these cells using the Nernst Equation a. Zn(s) | Zn² (0.10 M) || Cu²+ (0.010 M) | Cu(s) b. Mg(s) | Mg2+ (0.001 M) || Ag+ (2.0 M) | Ag(s) 33. Calculate the emf (another word for potential) of the following concentration cell at 25°C: Cu(s) | Cu² (0.080M) || Cu²(1.2M) | Cu(s) 34. A galvanic cell consists of a silver electrode in contact with 346 mL of 0.100 M AgNO3 solution and a magnesium electrode in contact with 288 mL of 0.100 M Mg(NO3)2 solution. Calculate E for the cell at 25°C. Objective 8: Describe the difference between voltage and current. 35. Define voltage. Are the metric units used to measure voltage? 36. Define current. Are the metric units used to measure current? 37. Describe the difference between voltage and current. 38. Voltage is also known by another name: electromotive force, or EMF. Explain what this other name for voltage means. 39. How many physical points must be referenced when speaking of the following electrical quantities? (a) Voltage (b) Current In other words, does it make sense to speak of voltage at a single point, or between two points, or between three points, etc.? Does it make sense to speak of current at a single point, between two points, between three points, etc.? 40. Suppose a battery outputs a voltage of 9 volts. Using algebra, calculate how many joules of energy are imparted to every individual electron moving through this battery. Students do not need to know how to complete this conversion for the quiz or exam, but it is a good practice to learn the relationship between volts and joules. 61
Objective 9: Describe and perform calculations associated with electroplating and electrodeposition. 41. A current of 10.7 amperes is run for 30.0 minutes through a cell whose reaction in the cathode is Cr³+ (aq) + 3e → Cr (s): a. How many coulombs of electricity pass through the cell? b. How many moles of electrons pass through the cell? c. How many moles of chromium are deposited? d. What is the mass of chromium in grams deposited? 42. Calculate the number of grams of copper metal that can be produced by supplying 1.0 mole of electrons (also referred to supplying 1.00 F) to a solution of Cu²+ ions. 43. Calculate the amounts of Cu and Br₂ produced in 1.0 h at inert electrodes in a solution of CuBr₂ by a current of 4.50 A. 44. A steady current was passed through molten COSO, until 2.35 g of metallic cobalt was produced. Calculate the number of coulombs of electricity used. 45. The passage of a current of 0.750 A for 25.0 min deposited 0.369 g of copper from a CuSO₁ solution. From this information, calculate the molar mass of copper. 46. A student wants to deposit 10.0 g of gold onto a ring from a solution of AuCl3. How long (in hours) must the student run a 0.750 A current to deposit the desired mass of Au? 47. Calculate the current required to plate out 25.0g of nickel from an aqueous solution of NiSO4 if the current runs for 6.00 hr. 48. An electroplating firm wishes to plate 14.5 g of Cu onto a pair of baby shoes from a Cu(NO3)2 solution. If a 2.45 A current is used, calculate the time required in hours. 49. In a certain electrolysis experiment, 1.44 g of Ag were deposited in one cell (containing an aqueous AgNO3 solution), while 0.120 g of an unknown metal X was deposited in another cell (containing an aqueous XCl3 solution) in series with the AgNO3 cell. Calculate the molar mass of X. 62
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