Question

(1)Sucrose, C12H22O11, reacts slowly with water in the presence of an acid to form two other sugars, glucose and fructose, both of which have the same molecularformulas, but different structures.
C12H22O11 + H2O ? C6H12O6 (glucose) + C6H12O6 (fructose)
The reaction is first order and has a rate constant of 6.2 ? 10-5/s at 35?C when the H+ concentration is 0.10 M. Suppose that the initial concentration of sucrose inthe solution is 0.40 M. What will the sucrose concentration be after 2.0 hours?

(2)The rate constant for a certain first-order reaction is 0.40/min. What is the initial rate in mole/L•min, if the initial concentration of the compound involved is0.50 mol/L?

(3)Sucrose, C12H22O11, reacts slowly with water in the presence of an acid to form two other sugars, glucose and fructose, both of which have the same molecularformulas, but different structures.
C12H22O11 + H2O ? C6H12O6 (glucose) + C6H12O6 (fructose)
The reaction is first order and has a rate constant of 6.2 ? 10-5 /s at 35?C when the H+ concentration is 0.10 M. Suppose that the initial concentration of sucrose inthe solution is 0.40 M. How many minutes will it take for the sucrose concentration to drop to 0.30 M

Answer 1

(1) ans:

for a firt-order reaction, the decay follows the following equation

[A] = [A0]e-kt

given, k = 6.2x10-5 /sec & [A0] = .4 M & [A] = .3M

substitute values we get

t = 4629.03 sec

Answer 2

(2) ANS:

For first order reaction: Initial rate = rate constant x initial concentration of compound k[compound] = 0.40 x 0.50 0.20 mol/L.min