All Free Chemistry MCQs with Answers

• A. vapourization
• B. solvent extractio
• C. filtration
• D. crystallization

Explanation: The correct answer is (d) crystallization.Crystallization: This process involves separating a solid from its hot saturated solution by…

• A. reducing agent
• B. oxidizing agent
• C. drying agent
• D. coloring agent

Explanation: rying agent in crystallization (option C):CaCl2 and PCl5: These compounds are known for their hygroscopic properties, meaning they have a…

• A. Filtrate, residue
• B. Dilute solution
• C. Residue
• D. both a &b

Explanation: The solution remaining after the formation of crystals is called Mother liquor (Option A):Mother liquor refers to the solution that…

• A. Around the thermometer
• B. In the condenser
• C. In the circulating water
• D. In the heated flask

Explanation: Distillation is described as a two-step process: Vaporization → Condensation. For vaporization to happen, you need a heat source.

• A. Around the thermometer
• B. In the condenser
• C. In the circulating water
• D. In the heated flask

Explanation: Distillation is used to separate a volatile liquid (like water) from a non-volatile solid (like magnesium chloride).

• A. Move the flask farther from the flame.
• B. Move the flask closer to the flame.
• C. Allow less air into the collar of the burner.
• D. Allow more air into the collar of the burner.

Explanation: An orange, sooty flame indicates incomplete combustion due to insufficient oxygen.

• A. 0.1 M
• B. 0.2 M
• C. 0.3 M
• D. 1 M

Explanation: Using the titration formula M1V1=M2V2 for the acid and base. Plugging in the values gives (0.1 M) (30 mL)= Mbase(15 mL).

• A. Add concentrated acid to water slowly, following the appropriate safety protocols.
• B. Add water to the concentrated acid slowly.
• C. Carefully return unused or excess chemicals to their original containers.
• D. Flush eyes with water at the eyewash fountain for at least 15 minutes, then report the accident for further help.

Explanation: Add concentrated acid to water slowly, following the appropriate safety protocols.

• A. The rule is to add concentrated acid to water slowly.
• B. The rule is to add water to the concentrated acid slowly.
• C. Carefully replace unused or excess chemicals into their properly labeled containers from which they came.
• D. Flush eyes with water at the eyewash fountain for at least 15 minutes, and then report the accident for further help.
• E. Dispose of chemicals in the proper places and following posted procedures. Do not return them to their original containers.

Explanation: You never return chemicals or solutions to their original containers for fear of contaminating the original source.

• A. The thermodynamics first law is not sufficient to predict the direction of the process
• B. In the case of an exothermic reaction, the overall enthalpy fo the products is greater than that of reactants
• C. for the reaction H2(g) + Br2 (l) → 2HBr (g) from the bond enthaly data, It is possible to calculate the value of H
• D. At 298K and 1 atmpressure, diamond's standard enthalpy is zero

Explanation: Only option A has correct statement. The first law of thermodynamics states that energy is conserved in any process.

• A. Propagation
• B. Free radical substitution
• C. Addition
• D. Elimination

Explanation: The correct answer is 'Free radical substitution.' This mechanism involves the substitution of hydrogen atoms in alkanes with halogen…

• A. (NH2)2CO
• B. NH2CH3
• C. C6H5NH2
• D. N(CH3)3

Explanation: Urea is organic compound which belongs to amide class

• A. H+, H, H-
• B. Li+, Na+, K+
• C. Cl-, Br-, I-
• D. F-, Ne, Na+

Explanation: soelectronic species are atoms or ions that have the same number of electrons.

• A. High energy trelecon beam
• B. α-particle
• C. X-rays
• D. All of the above

Explanation: Molecular ions are formed by passing high-energy electrons through a sample .High-energy electrons can ionize molecules by knocking off…

• A. Relative abundance
• B. Average mass of the element
• C. Number of isotopes
• D. Relative isotopic mass

Explanation: The number of peaks obtained in mass spectrometry corresponds to the number of isotopes of the element present in the sample.

• A. CH₂Cl₂
• B. CH₃Cl
• C. CCl₄
• D. CHCl₃

Explanation: Empirical formula gives the simplest whole-number ratio of atoms in a molecule.

• A. Isotopes with odd atomic number are abundant
• B. Isotopes with odd atomic number and even mass number are abundant
• C. Isotopes with even atomic number and even mass number are abundant
• D. Isotopes with even atomic number and odd mass number are abundant

Explanation: Isotopes with even atomic number and even mass number are abundant.There are several reasons why isotopes with even atomic numbers and…

• A. 2.24dm3
• B. 22.4 dm³
• C. 1.12 dm³
• D. 11.2 cm³

Explanation: To find the volume occupied by a gas at Standard Temperature and Pressure (STP), we can use the ideal gas law and the molar volume of a…

• A. 0.25
• B. 0.50
• C. 0.75
• D. 100

Explanation: One mole of CO2 has a mass of 44 g and 32 g of O2.So 16 g of O2 have 22 g of CO2 or 0.5 moles of it.Therefore, the mathematical…

• A. They possess different mass numbers
• B. They possess different physical properties
• C. They possess the same chemical properties
• D. They possess different positions in the periodic table

Explanation: This statement is incorrect. Isotopes of the same element share the same position on the periodic table because they have the same number…