1

### JEE Main 2019 (Online) 9th January Evening Slot

For the reaction, 2A + B $\to$ products, when the concentrations of A and B both were doubled, the rate of the reaction increased from 0.3 mol L$-$1s$-$1 to 2.4 mol L$-$1s$-$1. When the concentration of A alone is doubled, the rate increased from 0.3 mol L$-$1s$-$1 to 0.6 mol L$-$1s$-$1.
A
Total order of the reaction is 4
B
Order of the reaction with respect to B is 2
C
Order of the reaction with respect to B is 1
D
Order of the reaction with respect to A is 2

## Explanation

$r = K{\left[ A \right]^x}{\left[ B \right]^y}$

$\Rightarrow 8 = {2^3} = {2^{x + y}}$

$\Rightarrow x + y = 3\,...(1)$

$\Rightarrow 2 = {2^x}$

$\Rightarrow x = 1,y = 2$

Order w.r.t. A = 1

Order w.r.t. B = 2
2

### JEE Main 2019 (Online) 9th January Evening Slot

Consider the following reversible chemical reactions : The relation between K1 and K2 is :
A
K1K2 = ${1 \over 3}$
B
K2 = K13
C
K2 = K1$-$3
D
K1K2 = 3

## Explanation 3

### JEE Main 2019 (Online) 10th January Morning Slot

Which of the graphs shown below does not represent the relationship between incident light and the electron ejected from metal surface ?
A B C D ## Explanation

E = W + ${1 \over 2}$mv2

K.E. = hv $-$ 4v0

K.E. = hv + ($-$ hv0)

y = mx + $\underline C$
4

### JEE Main 2019 (Online) 10th January Morning Slot

Consider the given plots for a reaction obeying Arrhenius equation (0oC < T < 300oC) : (K and Ea are rate constant and activation energy, respectively) Choose the correct option :
A
I is right but II is wrong
B
Both I and II are correct
C
Both I and II are wrong
D
I is wrong but II is right

## Explanation

Arrhenius Equation -

Arrhenius gave the quantitative dependence of rate constant on temperature by the Arrhenius equation.

- wherein

$k = A{e^{ - {E_a}/RT}}$

${\mathop{\rm lnk}\nolimits} = lnA - {{{E_a}} \over {RT}}$

k = Rate constant

as we have learned in Arrhenius equation when we increase Ea, K should decrease As T increases, power of exponential increases so k also increase.

Hence, both the plots are correct.