4.

3. Consider a vertical plate of dimension 0.25m x 0.50m that is at T = 100 °C in a quiescent environment at T = 20 °C. In the interest of minimising heat transfer from the plate, which orientation, (A) or (B), is preferred? What is the convective heat transfer rate from the front surface of the plate when it is in the preferred orientation?

5. Consider the polymerization of styrene in toluene at 60°C initiated by di-t- byggside for a solution containing 0.04 mol of initiator and 2 mol of monomer per liter respectively. The initial rates of initiation, B., and propagation, B., are found to be 1.6x 10-10 Ms and 6.4 x 10 Ms", respectively, at 60°C. a. Cakulate and (5-points) b. Assuming no chain transfer, calculate the initial kinetic chain length. 6 points) c. Cakulate the conversion obtained after the reaction has gone for 5 h. (5 points) d. Assuming only disproportionation and under the conditions stated, the transfer constant of styrene, C, is 0.85 x 10%. How much does this transfer affect the molecular weight of the polymer? (5 points) e. The molecular weight of this polymer is too high. The desired molecular weight of this polymeris 40,000 g mol". How much CC14 (in g L") should be added to the reaction medium to attain the desired molecular weight?C, of CC14 is 9x 107 ¹. (5 points)

2. In an externally added acid catalyzed poly-esterification, the conversion increased from 98% to 99% in 82 minutes. Calculate an estimate of time that was needed to reach the 98% conversion. (15 marks) 3) Identify the steps involved in drawing the reaction pathway of a step polymerization reaction. (5 marks)/n1. Given 98.5% conversion of monomers with average molecular weight 150 g/mol, calculate Mw, Mn and PDI. (15 marks)

A straight rod of solid polymer is of length 1 m and diameter 10 mm. The polymer is linearly viscoelastic with a tensile creep compliance: D(t) = 2-exp(-0.1t), where t is in hours. The rod is suspended vertically and a mass of 10 kg is hung from it for 10 hours. A) Find the change in length of the rod. Express the result in mm, with two decimals. B) After 10 hours, the 10 kg mass is removed. Calculate the strain remaining in the rod after a further 10 hours. Express the result in percentage, with three decimals

2. Many olefins can be readily polymerized by a free-radical route. On the other hand, isobutylene is usually polymerized by a cationic mechanism. Explain. (10- points)

2. Describe each of the following processes - identify the required reagents, explain how the reactions happen and support with relevant mechanisms of reaction where possible. (10 points) r a. cationic polymerization b. anionic polymerization c. coordination polymerization

6. The efficiency of ABN in initiating polymerization at 60°C was determined by the following strategy. They measured B, and v and calculated B. - B₁/v. The constant kd was measured directly in the system, and from this quantity and the measured ratio B,/v the fraction f could be determined. The following results were obtained for different concentrations of initiator. Using k.-0.0388 h¹, evaluate f from these data. (where fis your radical efficiency factor). (10 points) [I] (gL¹) Rp/ × 10ª (mol L−¹ s¯¹) 0.377 1.57 1.72 6.77 0.0556 0.250 0.250 1.00 1.50 2.50 10.9 17.1

1. Pressurized liquid water is heated by flowing through a square tube with side length s = 10 cm andlength L = 15 m and whose surface is maintained at 235 °C. a. If the flow rate and inlet temperature of the water are 0.005 kg/s and 20 °C, what is the outlet temperature Tmo? What is the total heat transfer rate q for the tube? Assume fully developed flow.

3. A reaction has the rate of initiation of 1.5x107 Ms¹ and the rate of propagation of 7.8x 105 Ms¹¹. a. Determine the kinetic chain length (5-points) b. Determine the extent of reaction if the reaction was terminated by: i. Disproportionation ii. Combination iii. 50% disproportionation, 50% combination (5-points) (5-points) (5-points)

L 4. In a living polymerization, chain length simplifies to [M]/[I]o because all initiation leads to polymerization and there are no termination steps. Given a radical polymerization with [M] = 4.5 M and [I]o = 1.25 mM, compare chain length in the following situations: a. a living polymerization (5-points) = b. a non-living polymerization with f = 0.5; kpk = 0.003s-1; kg = 0.0001 s-1. (5-points) c. a non-living polymerization with f = 0.5; p = 0.003s-1; k= 0.3s-1; ka=0.0001 s-1. (5-points) d. a non-living polymerization with f = 0.5; p = 0.003s¹; k= 0.003s¹; ka=0.1s¹. (5-points)