Question

I need the best solution for these 2 questions on the section " Check your learning" (10.4 and 10.5) to prepare my exam in class. Thank you so much for helping me

Y althlon tai sok Translate Gm arch this book O Back Figure 10.20 Depending upon the relative strengths of adhesive and cohesive forces, a liquid may rise (such as water) or fall (such as mercury) in a glass capillary tube. The extent of the rise (or falt is directly proportional to the surface tension of the liquid and inversely proportional to the density of the liquid and the radius of the tube. The height to which a liquid will rise in a capillary tube is determined by several factors as shown in the following equation: 27 cos 0 TPB In this equation, h is the height of the liquid inside the capillary tube relative to the surface of the liquid outside the tube, T is the surface tension of the liquid, is the contact angle between the liquid and the tuber is the radius of the tube, p is the density of the liquid, and g is the acceleration due to gravity, 9.8 m/s. When the tube is made of a material to which the liquid molecules are strongly attracted, they will spread out completely on the surface, which corresponds to a contact angle of 0. This is the situation for water rising in a glass tube. EXAMPLE 10.4 Capillary Rise At 25 °C, how high will water rise in a glass capillary tube with an inner diameter of 0.25 mm? For water, T = 71.99 mN/m and p = 1.0 g/cm Solution The liquid will rise to a heighth given by: h = 27 cos The Newton is defined as a kg m/s, and so the provided surface tension is equivalent to 0.07199 kg/s?. The provided density must be converted into units that will cancel appropriately: p= 1000 kg/m'. The diameter of the tube in meters is 0.00025 m, so the radius is 0.000125 m. For a glass tube immersed in water, the contact angle is 8 0'. so cos 8 = 1. Finally, acceleration due to gravity on the earth is g -9.8 m/s. Substituting these values into the equation, and cancelling units, we have: 2 (0,07199 kg/s2) (0.000125 m) (1000 kg/m) (9.8 m/2y = 0.12 m = 12 cm Check Your Learning Water rises in a glass capillary tube to a height of 8.4 cm. What is the diameter of the capillary tube? ANSWER: diameter 0.36 mm

Answer 1

- h= peg g 2 T Cosó 8 Thea - 10.4 For capilary raise, we have h 2T Costa I h = height of water in the O capilary tube = 8.4 cm T = 84x10 m T= surface tension of water = 0.07199 kg/s2 12x To = contact angle between 0.07199 x Cos.o° / water and tebl=0 18:43 103 1000x958) paradies of cabeilary tebe I P = Density of water = 1.75*10 m. = 1000 kq Yus .. Diameter of the capilary / g = gravity on earth . tube. (a) = 28 = 2*1*75 xideme : 3.5x10m = 9.8 m/s2 - 35 mm Ans,

10.5 The intermolecular force of attraction between alcohol molecules is directly proportional to the surface area of the molecules because the van der Waal's force is depends only upon the surface area of the molecule. As the surface area increases from methanol to butanol as - CH3OH CH3 CH2OH(CH3 CH₂ CH₂OHL CH3 CH₂ CH₂ CH2OH .50 the intermolecular Van der Waal's Force of attraction also increases bom methanol to butanol. Again higher is the intermolecular force of attraction, lower is the tendency of the molecules to be in vabor phase is, higher is the intermolecular son force of allraction lower is the vapor pressure of the molecules. Hence, the vapor pressure of alcohols (given) decreases from methanol to betanol as - CH3OH) CH3 CH₂OH > CH3 CH2 CH2OHY CH3CH24420th cla 5.95 kPa 2.67 kPa 0.56 kPa