Test2_key_2007

Test2_key_2007 - Name: 250 Principles of Chemistry...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Name: 250 Principles of Chemistry Chemistry 107 (002) Test 2 Please show all work 'quids and gases to describe the key chemical we experience. HZQM3 ——3 Hz 0C?) b. Explain the energy flows associated w cooling. (Numbers are not necessary) enJo“ GW‘" L V7 tenoJL} (Jet-57 Cram bul‘r A, hula ith this reaction and how they cause the 2. (30 points) When we burn gasoline ( generated from the combustion reacti work to move the car forward. a. Is the reaction (combustion AH? approximate as octane, C8H18) in our cars the heat on expands the gas in the piston which then does the ) endothermic or exothermic? What is the sign for “endothermic 4/exothermic Sign " b. Write a balanced chemical equation for the combustion reaction associated with octane (CgH 13) reacting with 02 to form Com) and H200). I adhered to the Gustavus honor code: Signature c. If AHmmanon of octane is -249 kJ/mole and that of C02(g) and H20“) are given in the table at the end of the test, calculate AH for this reaction. Remember: AH = Hpmducts — Hreactams keeping track of coefficients from part b above. M": a in“; ‘8 who; ~ (5.3m ~ t- Mar/“1.) = («Mama/.45 Hex-393.5644; +‘w‘lA-JZML : - $970 («T/mole, OUR-Q“; d. If the density of octane is 2.66 kg/ gallon, how much energy is released from the burning of 1 gallon of gasoline? u) = I M 0 deg“; I q 3 mole’ ' Moi. (“‘90 ?/g,.ll.,\\ (W 3") : Z13 "496%,, .. L'IQO’XIOS kJ/gallon gasoline '3 “Ac .y.¢,3( ~5770 HT e. If we use ethanol (CszOH) produced from corn in our car we get -1367 kJ/mole ethanol combusted. Write a balanced chemical equation for this combustion reaction in a similar manner to part b above. H 2 o a ZCo C2 SORIQ) ‘1’ z; Let) 3 HLOC(} f. Comparing the ethanol and octane balanced reactions (b and e above) which produces more C02 per mole of fuel? 0&1“. $2 .25. § Z— mles (06 V4 {LAG/\ol Ll X morn g. If the density of ethanol is 2.987 kg/gallon what is the energy content in k] of a gallon of ethanol using the information from part e above? (am/MM m“) (—64.7 I‘Vnoch “IE 5 "‘ 853k!“ kJ/gallon h. Compare energy/gallon and C02 production between octane (gasoline) and ethanol. Use this to comment on the benefits of each fuel. ’ (“Haul “3.8% 0" - (0:115 Rig/Th” ml C0 OCLuu. 4.28 ypgk 3/30.!"4 I‘N% all..qu wart! k “"37 mic CO; e - PageZ 5‘“ 3. 4. (12 points) Consider an oxidation-reduction reaction. a. Is there a relationship between oxygen and oxidation? 0:93": 00m fervor) 0.5 cm await}; ageni’. b. Write out a reaction in which magnesium (Mg) reacts with oxygen (02) to form magnesium oxide. 0. Explain the role oxygen play in this reaction OX‘QQA i> oxflaml-l and (20 points) The following chemical reaction changes color from orange to blue when products are formed. The compounds containing chromium (Cr) are responsible for the color change and this color change has to do with the oxidation state of chromium. The first reactant is ethanol as found in alcoholic beverages. ,L 3CH3CH20H + ‘1 {'31:- £1? + 8HZSO4 3CH3COOH + zerggsogp + 2KZSO4 + 11HZO 47. .‘L "‘1 i; -—b a. If sulfate (8042') is a —2 charged polyatomic anion what are the two oxidation state of chromium? 3C'+ Cr a C(- a!“ch ° 4 b *1 b. Is chromium being oxidized or c. If a person breaths through a solution of K2C1‘207 and H2S04 what will we see and under what circumstances will this occur? “EC ulcsho‘ 0A / Nani-Co s 399 Cs ("-0ch ‘b If" "c Mu. c. col 0 P . (1. Identify an acid in the above reaction. H S0 H 9 r 3 v: Q ANLD.‘ 9t 0‘. a CI. 5. (12 points) We can assign the caloric content of foods by considering the parallel between combustion reactions and the net respiration of foods within our bodies. A fun(ny) example is shown below: Substance AHcombus,,-M(kJ/g) ___—___————— Apple —2 Beef -8 Beer -1.5 Gasoline —34 In the case of sucrose the net reaction is: CBH1ZO6 (s) + eo2 (9) —+ 6002 (g) + 6H20 (I) AH = -2801 kJ/mol .lf6 ki 26 ttl 'lth 7 f h ka a coo es( g 0a weigr) ave go sucrose, ow many 0 energy are contained? ID“! I i 73 = ‘Efimgnule Saw:er M kJ 1n 6 cookies no a/MLL b. Given that a food calorie is 1000 calories (1 kcal) and there are 4.184 J in l calorie, how many food calories are there in 1 cookie? ‘* Page 4 6. (12 points) Calcium ions are present in Saint Peter drinking water at reasonably high concentrations and their presence along with magnesium ions leads to the concept of “hard” water. The following precipitation reaction occurs: 2 2— Ca +(aq) + CO3 (aq) —> CaCO3(S) a. Why is this an undesirable reaction? Sold («Ml-c) Weevil-ul— on (der1i’lli03. 0035 (V6. b. When we use a water “softener” we substitute sodium ions for calcium ions using what is l<nown as an ion exchange column. What desirable change might we see after thus “softening”? Nalws“? i5 solublc, no (Heu'ptl’oal‘ Page 5 ...
View Full Document

This note was uploaded on 04/29/2008 for the course CHEM 107 taught by Professor Smith during the Fall '07 term at Gustavus.

Page1 / 5

Test2_key_2007 - Name: 250 Principles of Chemistry...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online