Using a graphical method for counter-current cascades 
    in a partially miscible system, streams exiting the same 
    stage (such as E1 and R1) are connected by 
    __________.
                         E           E
       extract             1           2
                    1          2
              R                        raffinate
                1        R
                           2
    A. the difference point
    B. equilibrium curve
    C. neither of these
   Given a constant liquid-liquid extraction partition 
   coefficient, the flow rates of solute (B) and liquid 
   carrier (A), how can one decrease the concentration of 
   B in the raffinate stream? 
   Assume equilibrium is reached at each stage.
  A. increase the tank size
  B. decrease the amount of solvent
  C. increase the amount of solvent
  D. recycle ½ of the raffinate to the feed
  A liquid-liquid extraction of a solute (B) in a feed carrier 
  (A) is performed using a solvent (S). Which of the 
  following, when doubled, will have the greatest impact 
  on increasing the fraction of B extracted?
  A. flow rate of A
  B. flow rate of S
  C. reciprocal of the partition coefficient
  D. mass ratio of B to the feed (A)
     Which of the following material balances is true for a 
     co-current liquid-liquid extraction with stage 
     equilibrium?
         R                R              R             R
           1               2              N              N+1
                 Stage          Stage         Stage 
         E         1      E       2     E       N       E
           0               1              N-1            N
     A. R = R
          1    2
     B. R + R = E + E
          1    2   0    1
     C. E + R = E + R
          0   1    1    2
     D. E + R = E + R
          0   2    1    1
     Vitamin E is isolated from a vegetable oil using hexane 
     in liquid-liquid extraction.  How may degrees of 
     freedom does this system have? The mixed feed 
     contains oil, hexane and vitamin E.
     A. 0                                             Extract
     B. 1          Mixed feed         Settling Tank
     C. 2           X wt.% oil        Temp = 25°C
                    Y wt.% C
     D. 3                    6
                    Z wt.% Vit.E                      Raffinate
     E. 4