Question

Question 1    :  
The reaction A(aq) ---> B(aq) is a first order reaction with respect to A(aq). The concentration of A(aq) is reduced to 33.1 % of its initial value in 1.54 minutes. What is this reaction's half-life (in s)?  

Question 2    :  
The reaction A(aq) ---> B(aq) + C(aq) is a first order reaction. The half-life of A(aq) is 91.0 s at 25.0^oC and its half-life is 69.2 s at 45.0^oC. What is its half-life (in s) at 65.0^oC?  

Question 3    :  
The half-life of ¹⁴C is 5730 years. A sample contains 91.3 % of the ¹⁴C that it would contain if it were still part of a living being. What is the age (in years) of this sample?

Answer 1

D A B A Btc First order ebst minuters- first order Half-life, tla = 0.693 0.693 K Aă Earth for a first order reaction, t= 2.303 log [A]. [A) from the given data, 1.54 minutes = 1.54x60 92.4 seconds 1 t'la 0.89* A. e Ferrer . At stod 25°c, th=915 Cie, 213+38=29815) 91=0.693x Axe 8.314+298 - ② Ea 92.4 - 2.303 16:31 At 45°C, t'la = 6242 69.25 - K= 2.303 Log 99.4 Lollos 0,331 69.2= 0.693 x A x Eu e 8-317* 318 - 0.0119685 : tla- 2.303 2.303 loy (1) I divided by 1 30.693 h elementazione 0.69 3x Axel F/8.314x318) qu 69.2 0.693 57.9 0.693 0.011968 seconds e 8.314 2298 91 69.2 318 2) i The reaction's half lif = 57.9 seconds Ea x 20 . 1.315= e 8.314 298x318 Dorfpi319) - Far 2.53116 - Ea (Activation energy) = 1008x10 ]

At 65c, 3 t% of 14 L = 5730 Ea B.3142333 years tl = 0.693* Axe we know, Divided by t= lalo th EL (-0.693) 8.693- A e 8314.298 91 t'a Eo 0,693x Axe 7314-335 lo 91.3 100 5730 91 tha 1.08.10 8.374 (-0.693) = e a 98 333 0.131341 x 5730 91 1.08610 x 40 8.314 297 338 220, - = e 152.58 years old 91 0.516 = e - 1.6753 6 tla = 91 1.6753 - 54.3185 Half life (ins) at 65°C - 54.318 seconds