All Free Chemistry MCQs with Answers

• A. Atomic Number
• B. Atomic Mass
• C. Molecular Mass
• D. Equivalent mass

Explanation: In 1914, he observed and measured the X-ray spectra of various chemical elements using diffraction in crystals.

• A. 2
• B. 3
• C. 4
• D. None

Explanation: Ethane thiol has the formula CH3- CH2- SH so the number of peaks of proton NMR are going to be 3

• A. C = C Bond
• B. C = O Bond
• C. C ≡ N Bond
• D. O - H Bond

Explanation: The carbonyl group (C=O) exhibits a strong absorption band around 1720 cm-1 due to the stretching vibration of the double bond between the…

• A. 0.8-2.5μm
• B. 16-1000μm
• C. 2.5-16μm
• D. 400-800μm

Explanation: Here are the approximate wavelength ranges for different portions of the infrared region:Near-infrared (NIR): 0.75 μm to 1.5…

• A. 24.32 amu
• B. 25.32 amu
• C. 26.32 amu
• D. 27.32 amu

Explanation: To calculate the average atomic mass, we use the formula:Average atomic mass=(Abundance1×Atomic mass1)+(Abundance2×Atomic…

• A. n → Π
• B. Π → Π
• C. 8 → 8
• D. n → 8

Explanation: This transition involves the excitation of an electron from a non-bonding orbital (n) to another orbital (8).

• A. Number of isotopes
• B. Mass number
• C. Relative abundace of isotopes
• D. Number of protons

Explanation: Option c is the correct answer. The height of a peak in a mass spectrum is directly proportional to the relative abundance of ions with…

• A. Ultraviolet
• B. Infrared
• C. Radio waves
• D. Microwaves

Explanation: Infrared radiation is involved in bond vibrations. When molecules vibrate, their bonds stretch, bend, and twist.

• A. 3200cm-1
• B. 1200cm-1
• C. 800cm-1
• D. 1720cm-1

Explanation: This is the correct answer. The characteristic signal of the carbonyl carbon in acetone (CH3COCH3) is typically found in the region around…

• A. Around 10-7 torr
• B. 1 torr
• C. Around 10-3 torr
• D. 10-7 torr

Explanation: Explanation:The pressure of these vapors is kept very low that 10-6 to 10-7 torr.

• A. De-Broglie
• B. Einstein
• C. Newton
• D. Rutherford

Explanation: Louis de Broglie's wave-particle duality theory was indeed influential in understanding the behavior of particles, including electrons.

• A. λ = hv
• B. λ = hp
• C. λ = h/2λ
• D. λ = h/p

Explanation: De-Broglie's wavelength equation, λ = h/p, relates the wavelength (λ) of a particle to its momentum (p) and Planck's constant (h).

• A. 1886
• B. 1887
• C. 1895
• D. 1885

Explanation: The study of hydrogen visible spectrum occurred in 1885. During this period, scientists were actively investigating the properties of…

• A. 1913
• B. 1919
• C. 1918
• D. 1905

Explanation: In 1913, Niels Bohr introduced his atomic model for hydrogen. He suggested that electrons move in fixed orbits around the nucleus, which…

• A. 2π/nh
• B. nh/2π
• C. n/2πh
• D. 2πn/h

Explanation: In Bohr's theory, only certain electron orbits are allowed where the angular momentum of the electron is quantized, meaning it can only…

• A. Rydberg
• B. Bohr
• C. Balmer
• D. Paschen

Explanation: The scientist who delved into the spectrum of hydrogen in the visible light wavelength range was actually (c) Balmer.

• A. Balmer series
• B. Lyman series
• C. Paschen series
• D. Brackett series

Explanation: (a) Balmer series: The Balmer series is the first series identified in the spectrum of hydrogen.

• A. 1685
• B. 1785
• C. 1985
• D. 1885

Explanation: The Balmer series was actually identified in 1885. It was a significant milestone in understanding the spectrum of hydrogen, shedding…

• A. Visible region
• B. Invisible region
• C. Ultraviolet region
• D. Infra-red region

Explanation: The Balmer series finds its home in the visible region of the electromagnetic wave spectrum.

• A. Newton
• B. Bohr
• C. Rydberg
• D. Planck

Explanation: In 1896, the results of spectra obtained by Balmer were expressed by Johannes Rydberg.