Short Questions in Chemical Engineering


1. Since radioactive decay is a first-order process, the decay rate for a particular nuclide is commonly given as the half-life. Given that potassium contains 0.0118% 40K, which has a half life of 1.27×109 years, how many disintegrations per second are there in a gram of KCl?

2. The decomposition of HI to H2 + I2 at 508°C has a half-life of 135 min when the initial pressure of HI is 0.1 atm and 13.5 min when the pressure is 1 atm. (A) Show that this proves that the reaction is second order. (B) What is the value of the rate constant in L mol-1s-1? (C) What is the value of the rate constant in bar-1s-1? (D) What is the value of the rate constant in cm3s-1?

3. The reaction between propionaldehyde and hydrocyanic acid has been studied at 25°C. In a certain aqueous solution at 25°C the concentrations at various times were as follows:

t/min                                   2.78       5.33       8.17       
[HCN]/molL-1                     0.0990    0.0906    0.0830       
[C3H7CHO]/molL-1             0.0566    0.0482    0.0406       
t/min                                 15.13      19.80       ∞       
[HCN]/molL-1                     0.0706    0.0653    0.0424       
[C3H7CHO]/molL-1             0.0282    0.0229    0.0000    

What is the order of the reaction, and what is the value of the rate constant k?

4. The rate constant for the reaction is

I + I +Ar → I2 + Ar

Is 0.59 ×1016cm6mol-2s-1 at 293K. What is the half-life of I if [I]0  = 2×10-5molL-1 and [Ar] = 5×10-3molL-1?

These questions belong to Chemical Engineering and they deal with radioactive decay of KCl, decomposition of HI to hydrogen and iodine, reaction between propionaldehyde and hydrocyanic acid and iodine and argon reaction and iodine half life.

Note: The solution is in handwritten format.


Download Full Solution


  • HWA

    this is a very good website

  • HWA

    I have 50 questions for the same test your page is showing only 28

  • HWA

    hi can you please help or guide me to answer my assignments. thanks

  • HWA

    hi can anyone help or guide me to my assignments. thanks

  • HWA

  • HWA

    This solution is perfect ...thanks

  • HWA

    Hello Allison,I love the 2nd image that you did! I also, had never heard of SumoPaint, is something that I will have to exolpre a bit! I understand completely the 52 (or so) youtube videos that you probably watched. Sometimes they have what you want, sometimes they don't! However, it is always satisfying when you are able to produce something that you have taught yourself. Great job!Debra 0 likes

  • HWA

    Perfect bank of solution. 

  • HWA

    great !

  • HWA
    Paul Brandon-Fritzius

    thanks for the quick response. the solution looks good. :)

  • HWA
    tina Johnson

    thnx for the answer. it was perfect. just the way i wanted it. 

  • HWA

    works fine.