koofer 2

koofer 2 - .\ I -t/ cfw_':-J Exam I Septemb er 14;2004...

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.\ I -t/ {':--J Exam I F'ORM A. EVEN l) What is the reason why hydrocarbons are not soluble in water? @;fn.y are hydrophilic. ffifr. C-H bond is nonpolar. @)rne C-H bond is polar. ,@ fn.y are too large to dissolve in water. \p They ioniZe when placed in water. 2) In a single molecule of water, the two hydrogen atoms are bonded to a single oxygen atom by hydrogen bonds. nonpolar covalent bonds. olar covalent bonds. ionic bonds. van der Wadls interactions. Septemb er 14;2004 NUMBERED SEATS Barstow y'Wn "nproperty of water is probably /most important for the functioning.of gganisms at the cell and molecular level? (A)_)bhesion and high surface tension ffiigrr specific heat ($trigh heat of vaporization buffering capacity yersatility as a solvent Question 6 is based on the cartoon of a solute molecules surrounded by a hydration shell of water. HHHH ,{p Hi HN -31- Why does ice float in liquid water? @fn. fiquid water molecules have more energy and can push up the ice. @ifne ionic bonds between the molecules Xt". prevent the ice from sinking. . (flIce always has air bubbles that keep it Aoat. ;Qfydrogen bonds keep the molecules of ice farther apart than in liquid water. @)fne crystalline lattice of ice causes it to E€ denser than liquid water. 4) What are hydrophobic substances? fA\on-ionic or nonpolar substances that fra water. @non-ionic or nonpolar substances that ,\]drogen bond with water. []f ionic or polar substances that repel water. ffiionic or polaf substances that attract \6ter. -'1b HH 6) Based on your knowledge of the polarity ,,af water, the solute molecule is most likely (@lositivelycharged M$Varophobic. lplneSativelycharged. fu)onpolan \@ neutral in charge. \- 7) Which of the following statements is true about buffer solutions? They @wiil always have a pU oiz. @)end to maintain a relatively constant pH. /tflmaintain a constant pH whbiii6ases are bi1O.a to them but not when acids are added to them. ,' @$,ur""a lowering 9f pH when acids are r-added to them. "ft5)r"rarely found in living systems. @*ot""nles that readily dissolve in water.
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8) The carbon present in all organic molecules has been recycled through other living hanisms thousands of times. is piocessed into sugars,through otosynthesis. is derived from carbon dioxide. A and C only ,BandC fi;r: r-(C* l3), A carbon skeleton is covalently both an amino group and a carbcixyl When placed in water, @rtwouldhrnclion only as an acid because of, .j{re carboxyl group. l(B) it would function only as a base because of /]f amino group. , (9 it would function as neither an acid nor a base. ! @t,
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koofer 2 - .\ I -t/ cfw_':-J Exam I Septemb er 14;2004...

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