JEE Main 2026 — Jan 23, Shift 2 — Chemistry solution

JEE Main2026Jan 23, Shift 2Chemistry

Identify the INCORRECT statements from the following:

A. Notation $_{12}^{24} M g$ represents 24 protons and 12 neutrons.

B. Wavelength of a radiation of frequency $4.5 \times 1 0^{15} s^{- 1}$ is $6.7 \times 1 0^{- 8}$ m.

C. One radiation has wavelength = $λ_{1} (900 nm)$ and energy = $E_{1}$ . Other radiation has wavelength = $λ_{2} (300 nm)$ and energy = $E_{2}$ . $E_{1} : E_{2} = 3 : 1$ .

D. Number of photons of light of wavelength $2000$ pm that provides 1 J of energy is $1.006 \times 1 0^{16}$ .

Choose the correct answer from the options given below:

A
A and D only
B
A and C only
C
A and B only
D
B and C only

Solution

(A) The notation $_{12}^{24} M g$ uses the lower number as atomic number (protons = 12) and the upper number as mass number (24). So it represents 12 protons and $24 - 12 = 12$ neutrons. The statement reverses them. Incorrect.

(B) $λ = \frac{c}{ν} = \frac{3 \times 1 0 ^{8}}{4.5 \times 1 0 ^{15}} = 6.67 \times 1 0^{- 8}$ m. Correct.

(C) $E \propto \frac{1}{λ}$ , so $\frac{E _{1}}{E _{2}} = \frac{λ _{2}}{λ _{1}} = \frac{300}{900} = \frac{1}{3}$ , i.e. $E_{1} : E_{2} = 1 : 3$ , not $3 : 1$ . Incorrect.

(D) $n = \frac{E \cdot λ}{h c} = \frac{1 \times 2000 \times 1 0 ^{- 12}}{6.626 \times 1 0 ^{- 34} \times 3 \times 1 0 ^{8}} \approx 1.006 \times 1 0^{16}$ . Correct.

Incorrect statements: A and C.

← Back to full paper

Practice more Chemistry

Concept-wise practice with instant solutions on Fundamenthol.

Start practicing →