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Download CHEM 1201 (Basic Chemistry) – Exam 5 Form 2 | LSU Trusted Prep Guide with Correct Answers and more Exams Chemistry in PDF only on Docsity!
Exam 5 Form 2 MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A vessel contains a mixture of 26.0 grams of H2 (g) and 18.2 grams of CH4. If the total 1) pressure inside the vessel is measured at 2.24 atm, the partial pressure of Hg (g) must be atm. A) 4.15 1mol H, 26.0 g H, * =~>—— = 12.9 Mol H. B) 31.4 ge" 202 gH, 2 C) 0.181 D) 2.06, 1 mol CH, 18.2 g CH, * ———— = 1.13 Mol CH, E) 28.9 9 OMs* 76.04 g CH, 4 Part 12.9 mol Py = = 2.24 atm = 2.06m A, Whole ¢ (12.9 mol+1.1 mol) a 06 mol 2) Calcium hydride (CaHg) reacts with water to form hydrogen gas: 2) Calla (s) + 21120 () @ Ca(OH) (aq) + 212 (g) 2g 45.0 L, 0.995 atm, 32 °C How many grams of CaHg are needed to generate 45.0 L of Hg gas at a pressure of 0.995 atm and a temperature of 32 °C? Fi P Reaction problem: need to get to moles A) 75.3 7 5 ii Moles from PV=nRT for gases fe) 5) PV 0.995 atm «45.0L D) 0.894 n(Hz) = Rr Laon = 1.79 mol H, 5 533 0.08206 2% « (32 + 273.15)K 1 molCaH,) 42.094 g Call omar, See = 37.6 9 Catt, 2 mol H2 1molCaH, 3) Which one of the following should have the lowest boiling point? 3) B) Lil The lowest boiling point will have the weakest O) Hg0 intermolecular forces D) CgH5COOH CH4 only has dispersion forces. F) PClg The other molecules are polar, have H-bonding, or are ionic compounds 4) List the compounds in decreasing boiling point order. 4) CH30 CH3 kr CH3CN Al Re > CHBEN =CH30 CHS The lowest boiling point will have the weakest B) CH30 CHg > Kr > CH3CN intermolecular forces. C) CH30 CH3 > CH3CN > kr It would help to draw the Lewis structures for this one. CH3CN and CH,OCH, are both polar molecules, BUT the D) CHBCN > C CH,CN is more polar than CH,0CH, because of the E) Kr > CH3O CHg > CH3CN distribution of the dipoles. Consequently, CH,CN has the highest BP, then CH,OCHs, and then Kr which only has dispersion forces. 5) What is the predominant intermolecular force in NaNO3? 5) A) ion-dipole attraction B) London-dispersion forces D) hydrogen bonding E) dipole-dipole attraction NaNO, has a metal and would have ionic bonding. 9) A pressure of 0.750 atm is the same as a pressure of torr. 9) A) 760. B) 29.9 C) 33.0 D) 570. 760. torr E) 193 0.750 atm * = 570. torr 10) Which one of the following substances will have hydrogen bonding as one of its 10) intermolecular forces? A) 0) I H,C— C— CF, D) 11) What is the predominant intermolecular force in SiH4? A) hydrogen bonding ry H B) ion-dipole attraction HiSitH or H—Si—H C) dipole-dipole attraction ft D) ionic bonding a E c 0 Nonpolar molecule: dispersion forces only 1.5 P(atm) jo] 0.5 7 B R 0 a or L 1 14 -10 0 10 20 30 40 50 60 7% TCC) 12) The phase diagram of a substance is given above. This substance is a at 0.0 °C and 1.0 atm. A) liquid C) gas D) supercritical fluid E) crystal 11) 12) 16) Assign the appropriate labels to the phase diagram shown below. 16) latm4 0.006 4 atm T T —-3 0.01 25 100 T A) A= gas, B = liquid, C = solid, D = triple point B) A = liquid, B = solid, C = gas, D = triple point D) A = liquid, B = gas, C E) A= solid, B = gas, C = liquid, D = triple point olid, D = triple point 17) In liquid ethanol, 17) CH3CH20H which intermolecular forces are present? A) Only dipole-dipole and ion-dipole forces are present. B) Only dispersion and dipole-dipole forces are present. D) Only hydrogen bonding forces are present. 18) A gas originally at 27 °C and 1.00 atm pressure in a 3.4 L flask is cooled at constant 18) pressure until the temperature is 11 °C. The new volume of the gas is L. A) 3.6 B) 3.2 V1 v2 ©) 0.24 ri F2 D) 0.27 v1 1.00 241 =V1 __ 1.00 atm +2. - E) 3.4 V2 = Tile T2= ORoRaTSR (11 + 273.15)K =2.3L 19) A fixed amount of gas at 25.0 °C occupies a volume of 8.66 L when the pressure is 629 19) torr. Use Charles's law to calculate the volume (L) the gas will occupy when the — temperature is increased to 145 °C while maintaining the pressure at 629 torr. A) 1.49 B) 50.2 v1 _ v2 ©) 6.17 Tl =T2 E) 10.1 V2 = S86" _ s (121 + 273.15)K = 1144 ) 10. ~ (254273.15)K i on a 20) A sample of Ng gas (2.0 mmol) cffused through a pinhole in 5.5 s. It will take 20) s for the same amount of CHq to effuse under the same conditions. A) 3.1 — 2.0 mmol N, ri(N2) _ [M2 (CH,) Bee TW) =e r2(CH,) | M1 (N,) C73 D) 5: mmol a SD = 0.36 N, — r1(N,) _ |16.04 ) ay (CH,) 28.01 r1 (N. eesung = 0.755 r2 (CH,) 36 oe = = (0.755 72 (CH,) 36 mmol Use as a conversion factor to get to time 755 772 (CH) 12 (CH,) = 48 mmol/s isec 8 ee 2mmol CH,* Ta = 4.2 sec 
