表面与界面化学试卷(a)2005.doc

武汉理工大学考试试题纸（ A 卷）课程名称 表面与界面化学专业班级 材化0301，0302题号一二三四五六七八九十总分题分2423101091212100备注: 学生不得在试题纸上答题(含填空题、选择题等客观题1. Please explain the following terms: (38=24 points) surface tension CMC solubilisation interface coverage unit mesh surface atom density surface activity2. Figure 1 shows a unit cell for a cubic crystal structure. Please find the Miller index for the shadow plane, calculate the face atom density, and plot its unit mesh. (15 points)Fig.1 Unit cell for a cubic crystal structure If the latent heat of vaporization of the cubic solid is DHv, Please estimate the surface energy for the shadow plane. (8 points)3. At 77K a 1.5g sample of a porous solid showed the following results for the adsorption of nitrogen:P (kPa) 4 20V (cm3) (STP) 100 150If the saturated vapor pressure and molecular area of nitrogen at this temperature are 100kPa and 16.210-20m2, respectively, calculate a specific surface area forthe solid. (10 points)4. Figure 2 shows a number of adsorption isotherms (where a single isotherm is a coverage-pressure curve at a fixed temperature). Please determine the heat of adsorption at a given coverage. (10 points) Fig. 2 adsorption isotherms5. (1) Please give the conditions of contact angle for spreading wetting, adhesional wetting and immersional wetting. (6 points) (2) The HLB values for glyceryl monostearate and triethanolamine oleate are 3 and 12, respectively. Please point out which one is more soluble in oil? (3 points)6. During the CO oxidation on Pd(110) surface, the LEED pattern of O adsorption observed changes from Pd(110)c(24)O to Pd(110)(12)O with the temperature increase. Please draw the two LEED patterns and the possible real space overlayer structures for O on Pd(110). (Pd is a fcc metal). (12 points)7. At 20C the surface tensions of water and n-octane are 72.8 and 21.8 mNm-1, respectively, and the interfacial tension of the n-octane-water interface is 50.8mNm-1. Calculate(a) the work of adhesion between n-octane and water;(b) the work of cohesion for (1) n-octane and (2) water;(c) the initial spreading coefficient of n-octane on water. (12 points) 武汉理工大学教务处 试题标准答案及评分标准用纸 课程名称表面与界面化学 （ A 卷）1. surface tension: Surface tension is defined as the force acting at right angles to any line of unit length on the liquid surface or surface tension is the work required to increase the area of a surface isothermally and reversibly by unit amount. (3 points) CMC: CMC is the concentration above which micelle formation becomes appreciable. (3 points) solubilisation: Surfactant solutions above the CMC can solubilise otherwise insoluble organic material by incorporating it into the interior of the micelles. This is known as micellar solubilisation. (3 points) interface: The point, area, or surface along which two substances or other qualitatively different things meet. (3 points) coverage: a measure of the extent of adsorption of a species onto a surface. Usually defined as , Where Nads is the number of adsorbate atoms per unit area and Nm is the number of atoms adsorbated per unit area to produce one complete layer on the surface. (3 points) unit mesh: the unit cell of a two-dimensional surface structure. (3 points) surface atom density: the number of atoms per unit surface area。 (3 points) surface activity: The strong adsorption of such materials at surfaces or interfaces in the form of an orientated monomolecular layer is termed surface activity. (3 points)xyz2. (1) (a) Intercepts: a,a,. (b)Reciprocals: 1/a,1/a,0.(c) Multiply by a: 1,1,0So the Miller index is (110). （5 points）(2) the (110) face contains two atoms per unit cell. The area of the (110) unit cell face is 21/2a2. So the face atom density Ns=2/(21/2a2)= 21/2/a2（5 points）(3) the unit mesh is shown in the following figure as dashed lines. （5 points） (4) The CN in a bcc crystal is 8 (2 points). So, we can estimate the value of the energy Eb required to break each M-M bond as , where NA is the Avogadro number(2 points). If we were to separate the bulk and form two (110) planes each with Ns surface atoms, the two bonds would be broken per surface atom(2 points). The surface energy, g, is therefore given by (2 points)3. P/(V(P0-P)104 (cm-3) 4.17 16.67P/P0 0.04 0.2The slop and the intercept are 0.0078125, 0.0001045 respectively. (3 points) Vm=1/(0.0078125+0.0001045)=126.31 cm3 (3 points)The specific sruface area A=N0sVm/m22400=6.02102316.210-20126.31/1.5/22400=367m2/g (4 points)4. Read off a number of pairs of values of pressure (P) and temperature (T) which yield the same surface coverage, (5 points) and then plot a line of ( ln P ) vs (1/T), the slope of which yields the adsorption heat. (5 points)5. (1)In spreading wetting, the contact angle should be zero. (2 points)For adhesion wetting, the contact angle should less than 180 degree (2 points)For immersional wetting, the contact angle should less than 90 degree (2 points) (2)glyceryl monostearate. (3 points)6. The real space overlayer structures for c(24) and (12) are shown in the Fig.(a) and Fig.(b), respectively. (a) (3points) (b) (3points)O atomsPd atomsThe corresponding LEED patterns are shown as Fig (c) and Fig.(d) (c) (3 points) (d) (3 points)O spotsPd spots7. (1) the work of adhesion Wa= gw+gO-gwO=72.8+21.8-5