practiceexam18 - City College, Chemistry Department...

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Unformatted text preview: City College, Chemistry Department Chemistry 10301, sections T, T2, 3 Prof. T. Lazaridis Second Midterm exam, Nov. 6, 2007 Name (last name first): ____________________________________ I.D. Number last 4 : _______________________________________ Workshop leader: ________________________________________ Note: There are 7 questions in this exam (check both sides of the sheet). Fill in your answer in the blank space provided immediately following each question. 1/2 point will be subtracted every time you report a numerical result with an incorrect number of significant figures. The last sheet of this exam contains information that may or may not be needed to answer these questions. 1. (20) a. (5) How many ml of stock solution are needed to make 320 ml of 1.5 M HNO 3 solution from 16 M HNO 3 stock solution? VdMd = VcMc => Vc= VdMd/Mc = 320 ml X 1.5 M/ 16 M = 30 ml b. (5) The solubility of DDT has been estimated as 5.0X10-5 g/100 g of water. Express this solubility in parts per million. 5.0X10-5 g/100 g X 10 6 ppm = 0.5 ppm c. (5) An average pair of human lungs contains about 3.5 L of air after inhalation and about 3.0 L after exhalation. If the temperature is 37 o C and the pressure is 1.0 atm, how many moles of gas will be present in the lungs (a) after inhalation and (b) after exhalation? [assume ideal gas] n= PV/RT = 1 atm X 3.5 L / 0.082 (atm L/mol K) (37+273) K = 0.14 mol (after inhalation) n= PV/RT = 1 atm X 3.0 L / 0.082 (atm L/mol K) (37+273) K = 0.12 mol n= PV/RT = 1 atm X 3....
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practiceexam18 - City College, Chemistry Department...

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