T3-474747-s10-elab

T3-474747-s10-elab - T3-474747-s10 Question 1Allison...

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Unformatted text preview: T3-474747-s10 April 12 2010Question 1Allison prepares a glucose solution by putting a teaspoon (4.8 g) of sugar (C12H22O11; M=342 g/mol) in a cup and adding enough water that the resulting homogeneous mixture has a volume of 100 mL. 4.8 [g] /342 [g/mol] 0.14 [mol]. Concentration [sugar] = 0.014mol/0.1 L = 0.14M25 mL* 14 [mol/L]= 25 mL* 14[mmol/mL] = 3.5 [mmol] = .0035 [mol]•What is the concentration of the solution? •How many moles of sugar are contained in 25 mL of the solution?A. [sugar]= 0.14 M; 25 mL contains 0.0035 moles of sugarB. [sugar]= 0.014 M; 25 mL contains 0.00035 moles of sugarC. [sugar]= 0.14 M; 25 mL contains 0.0056 moles of sugarD. [sugar]= 1.4 M; 25 mL contains 0.056 moles of sugarE. None of the aboveQuestion 2There is one dark one in the middle plus 4 on the edges counting for ½ (as they are shared with the neighbors) Total 3 dark per cell. There are 4 open circles on the corner that each count for ¼ as they straddle four adjacent cells. So 3 dark and one openActually if you choose the origin between the circles it is even easier.Consider the above pattern with two-dimensional translation symmetry. Draw a suitable unit cell and select the correct statement.A. The unit cell contains seven filled and two open circlesB. The unit cell contains eight filled circles and one open oneC. The unit cell contains four open circles and five filled onesD. The unit cell contains one open circle and three filled onesE. None of the aboveYou may assume that the above pattern is entirely rectangular and that it continues in all directions.I was very disappointed on this question. This is the absolute easiest example I could come up with and we had done a harder one in class. Still many people gave terrible answers.Question 3Consider the following solid substances: 1)solid carbon dioxide (CO2)2)a quartz (SiO2) crystal3)a piece of tungsten metal (W)4)an ice cube (H2O)All these can evaporate when heated sufficiently, but the boiling points vary enormously. Consider the value of the heats of vaporization ΔvapH and which type of interaction is mostly responsible for this value. Select the best answer.A.ΔvapH for W is much larger than that of H2O because tungsten has metallic bonding and ice only hydrogen bonding. TrueB.ΔvapH for CO2 is only a little smaller than that of SiO2 because both are molecular solids kept together by dispersion forces. FALSEC. Both quartz and tungsten have large values for ΔvapH, but for different reasons: one is a covalent network (quartz) the other a substance with strong metallic bonding. covalent network (quartz) the other a substance with strong metallic bonding....
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This note was uploaded on 06/10/2011 for the course CH 101 taught by Professor Bigham during the Spring '08 term at N.C. State.

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T3-474747-s10-elab - T3-474747-s10 Question 1Allison...

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