General Chemistry - Final Exam 05

General Chemistry - Final Exam 05 - CHM 1300 and CHM 1310 B...

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CHM 1300 and CHM 1310 B DATE: December 15, 2005 Dr. Rashmi Venkateswaran 7:00 pm TIME: 3 hours Page 1 of 21 FULL STUDENT NAME: (Print) ____________________________________________ STUDENT NUMBER: ___________________________________________________ COURSE CODE: (Please circle) CHM 1300 CHM 1310B INSTRUCTIONS: 1. Write your answers on the exam. Please BOLD or HIGHLIGHT your final answer. 2. You are allowed to use electronic calculators during the exam (TI 30X, TI 34, TI 36). 3. Standard Potentials are on page 18. Equations and constants are given on pages 19 and 20. A periodic table of the elements is included (page 21). 4. Use the correct number of significant figures at all times. 5. Marks allotted to each question are shown in brackets. 7. Use the back of sheets for rough work. Three extra (blank) pages (15, 16 and 17) have also been included. 8. You are advised to read through the exam paper before you begin to write. Answer first those questions that you can do right away, proceeding to more difficult questions thereafter. Allow about ten minutes near the end of the exam period to read quickly through your answers, checking for obvious errors. Quest . 1 2 3 4 5 6 7 8 9 10 Marks /10 /5 /15 /10 /10 /11 /8 /11 /10 /10 /100
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page 2 of 21 (10) 1. (a) Small helium-neon lasers emit 1.0 mJ/s of light at 634 nm. How many photons does such a laser emit in one minute? (b) It requires a minimum of 216.4 kJ/mol to remove an electron from a potassium metal surface. i) What is the longest wavelength of light that can do this? ii) If UV light at 255 nm strikes this surface, what is the maximum speed of the ejected electrons?
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page 3 of 21 (c) A single pulse of a laser yields an average of 5.00 × 10 18 photons with a wavelength of 633 nm. If melting ice to water at 0 ° C requires 6.01 kJ/mol, what is the fewest number of laser pulses need to melt 10.0 g of ice? (5) 2. Breathalyzers determine the alcohol content in a person’s breath by a redox reaction using dichromate ions: C 2 H 5 OH (aq) + Cr 2 O 7 2- (aq) CH 3 COOH (aq) + Cr 3+ (aq) a) Balance this reaction. b) If a breath sample generates a concentration of 4.5 x 10 -4 M Cr 3+ in 50.0 mL of solution, what mass (in mg) of alcohol was in the sample?
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page 4 of 21 (15) 3. GeF 4 , SeF 4 , and XeF 4 all have similar formulae. (a) Draw the Lewis structures of these three molecules. Show your reasoning. (b) Determine the molecular geometry of the three molecules. (c) What is the shape of each of the three molecules? (d) Determine the formal charges on all the atoms in all three compounds.
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page 5 of 21 (10) 4. (a) The measured voltage of the cell Pt(s) | H 2 (g) (1.0 atm) | H + (aq) (x M) || Ag + (aq) (1.0 M) | Ag(s) is 1.02 V at 25 ° C. i) Write the balanced equation for the spontaneous cell reaction. ii) Which electrode is the anode and which is the cathode and what are their signs (positive, negative)? iii) Calculate the pH of the solution. iv) Draw a simple diagram of the cell.
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page 6 of 21 (b) Electrochemistry can be used to measure electrical current in a silver coulometer, in which a silver cathode is immersed in a solution containing Ag + ions. The cathode is weighed before and after passage of current. A silver cathode initially has a mass of 10.77 g and its mass increases to 12.89 g after current has flowed for 15.0 minutes. Calculate the current in amperes.
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This note was uploaded on 01/16/2011 for the course CHM 1300 taught by Professor Venkataswaren during the Fall '08 term at University of Ottawa.

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General Chemistry - Final Exam 05 - CHM 1300 and CHM 1310 B...

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