Chemistry Test 25

Result

Chemistry Test 25

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Weekly Quiz Competition

Question 1
4 / -1

Reaction rates are determined by all of the following factors except:

A
the number of collisions between molecules

B
the force of collisions between molecules

C
the orientation of collisions between molecules

D
the spontaneity of the reaction

Solution

Reaction rates are determined by all of the following factors

(i) the number of collisions between molecules

(ii) the force of collisions between molecules and

(iii) the orientation of collisions between molecules.

so, the spontaneity of the reaction is the correct option.
Question 2
4 / -1

In a first order reaction, the concentration of the reactant, decreases from 0.8 M to 0.4 M in 15 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M is

A
7.5 minutes

B
15 minutes

C
30 minutes

D
60 minutes

Solution

0.8 M to 0.4 M 15 min t_1/2

0.10 ï 0.050 1/2 ï 0.025

2 × t_1/2 = 30 min
Question 3
4 / -1

Consider the reaction, 2A + B → Products. When concentration of B alone was doubled, the half-life did not change. When the concentration of A alone was doubled, the rate increased by two times. The unit of rate constant for this reaction is

A
mol L^–1s^–1

B
s^–1

C
L mol^–1s^–1

D
no unit

Solution

When concentration of B is doubled, the half- life did not change, which means reaction is of first order w.r.t B. When concentration of A is doubled, reaction rate is doubled which means reaction is first order w.r.t A.

Hence overall order of reaction is 1+1=2.

So, unit of rate constant is L mol^–1s^–1.
Question 4
4 / -1

The plot of log k versus 1/T is linear with a slope of

A
E_a/R

B
ïE_a/R

C
E_a/2.303 R

D
ïE_a/2.303 R

Solution

The variation of rate constant is given by k = A exp(ïE_a/RT) or log k = log A

ï E_a/(2.303 RT). The slope of plot of log k versus 1/T is ïE_a/2.303 R.