Physical Chemistry Answers

The optical rotations of sucrose in 0.5 M HCl measured in seconds at 0, 20 and ∞ are +32.4, +25.5 and -11.1 respectively. Determine the order of the reaction.

. The half-life for the first-order decomposition of N2O5 is 2.05 x 104 s. How long will it take for a sample of this compound to decay to 80% of its initial value?

. A first-order reaction is 60% complete at the end of 90 min, what is the value of rate constant in sec-1?

The rate constant of a zero-order reaction is 0.2 (mol/L) hour-1. What will be the initial concentration of the reactant if after an hour its concentration is 0.089 mol/L?

Catalyzed reactions are faster because:
a. The concentrations are higher
b. The temperature is higher
c. The mechanism is different
d. None of the above

. The reaction: A → B follows first-order kinetics. The time taken for 0.8 mol of A to produce 0.6 mol of B is 1 hour. What is the time taken for conversion of 0.9 mol of A to produce 0.675 mol of B?

4. The rate of a reaction doubles when the concentration of one of the reactants is doubled.
In terms of the concentration of this reactant, the reaction is:

1. For a certain first order reaction, it is found that it takes 156 seconds for the concentration of reactant to fall from 0.100 M to 0.0500 M. How much time would it take for the concentration of reactant to fall from 0.0500 M to 0.0250 M?

100mL of oxalic acid requires35mL of 0.04 M KMnO4 to titrate it to the end point. Calculate the molarity of the oxalic acid.?

Question 18 : Rusting of iron Is an example of________ reaction
Fast
Slow
explosive
Moderate

Question 19 : Which of the following statements about the kinetics of the reaction
H
2
(
g
)
+
B
r
2
(
g
)
→
2
H
B
r
(
g
)
H2(g)+Br2(g)→2HBr(g)
is definitely true?
The presence of hydrogen bromide, HBr, inhibits the rate of the reaction
The reaction is first order with respect to bromine, Br2.
It is not possible to determine anything about the kinetics of the reaction from the stoichiometry.
The reaction is second order overall.

Question 20 : Rate of reaction is defined as the
None of the above
Rate of change of conc. of product only
Rate of change of conc. of reactant only
Rate of change of concentration Of either reactant or product per unit time