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1 CE 350 Exam 1, Fall 2006 Print Name: Show all work to receive full credit. Required Signature. By signing on the line below, you pledge that you have not received help on this exam from any other person (other that the TA for clarification) and that the work handed-in by you is your work only. Your exam will not be graded without signing. Signature Equations: q c = Change in Stored Heat = m cv or p T t Work Tc η = η max = 1 Q T h h ( ) A T T q = R 1 2 Conversion Factors and Constants: 1 kcal 1Btu kj = = o o o kg C lb F kg C Btu 1 Watt = (Power = energy/time) hr K = o C R = o L atm F R gas = K mol For a pure gas at 1 atm and 25ºC: 1 mol = L Some conversion factors for problem 1: 24 grains = 1 pennyweight 20 pennyweight = 1 ounce 12 ounces = 1 pound 1 pound = grams 1. (5 pts) How many grains of calcium (Ca 2+ ) are there in 1.0 liter of water that contains 200 mg / L Ca 2+? page 1 of 5

2 2. (5 pts) A gas sample is 0.025% by volume methane (CH 4 ) at 1 atm total pressure and 25 ºC. What is the concentration of methane in units of mg/m 3. Recall for a pure gas at 1 atm pressure and 25 ºC: 1 mol = L. The atomic weight of carbon is 12, and of hydrogen is (10 pts) Briefly describe (define): a) The First Law of Thermodynamics: b) The Second Law of thermodynamics: c) Convective heat transfer d) HCO 3 - (what chemical species is this?) e) Beta particle f) nuclear fission page 2 of 5

3 4. (5 pts). The rate constant for decay of chemical X in water is 0.25 day -1 (0.25/day). What is its half-life under these same conditions? 5. (5 pts). A chemical partitions between lake sediment particles and water with an equilibrium partition coefficient equal to K p = 200 (mg/kg)/(mg/l). If the concentration on the sediment particles is 30 mg/kg, what is the concentration in water at equilibrium? 6. (10 pts) At the confluence of Streams A and B, stream C is formed. Given the data shown on the figure for Streams A and B, calculate the concentration (mg/l) of the chemical in Stream C, assuming the chemical is a conservative substance. Steam B Q 1 = 30 m 3 /sec C 1 = 10 mg/l Stream A Q 2 = 70 m 3 /sec C 2 = 5 mg/l C 3 =? Stream C page 3 of 5

4 7. (10 pts) Give the molecular formula and structure of each. Draw all hydrogen atoms in the structures. a) n-butane d) 2-methyl-2,4-dichlorohexane b) acetic acid e) 1,3-dichlorobenzene c) toluene f) ethanol 8. (10 pts) The ph of the Wabash River is 7.5. What fraction of ammonia in the river exists as ammonia (α NH3 ). Recall the total amount equals the sum of the species: ammonia (NH 3 ) and the ammonium ion (NH 4 + ). The pk a of NH 4 + is 9.3. page 4 of 5

5 9. (5 pts) A lake has a constant volume, V, and is fed by a stream that has a constant concentration (mg/l) of chemical, C. The flow rate into the lake from the stream, Q in, equals the flow rate out of the lake, Q out, and the lake can be assumed to be completely mixed. Chemical C decays in the lake, with a first order rate constant equal to k. Write the general mass balance equation for chemical C within the lake, and solve for the steady-state concentration of the chemical in the lake ([C] =?) in terms of other parameters and constants. dc Start with: V = dt 10 (10 pts) Balance the following equation using the lowest whole numbers. What is the theoretical oxygen demand of 20 mg/l C 3 H 5 O? Calculate your answer in units of mg/l O 2. The atomic weight of carbon is 12, hydrogen is 1, and oxygen is 16. C 3 H 5 O + O 2 CO 2 + H 2 O page 5 of 5