Free Experimental Techniques in Chemistry MCQs with Answers

31. What is the main purpose of chromatography in chemistry?

• A. To burn a substance
• B. To separate components of a mixture
• C. To dissolve solids in liquids
• D. To change the color of a solution

Explanation: Chromatography is a method used to separate and identify different substances in a mixture based on their movement on a stationary phase. It does not destroy or chemically change the compounds.

32. The given diagram shows steps of crystallization. In step C what is the main reason for leaving the solution to cool slowly?

• A. To form larger, purer crystals
• B. To increase solubility
• C. To speed up evaporation
• D. To prevent crystallization

Explanation: Slow cooling allows orderly arrangement of solute particles. forming large and pure crystals.

33. In simple distillation, the thermometer is placed:

• A. In the distillation flask
• B. Above the condenser
• C. At the mouth of the condenser
• D. In the receiver flask

Explanation: The thermometer measures the temperature of the vapors entering the condenser. This temperature corresponds to the boiling point of the liquid being distilled. Correct placement ensures accurate identification of the distilling component.

34. What should you do if a chemical splatters into your eyes?

• 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: The immediate first-aid for a chemical splash in the eyes is to flush them with a large amount of water for at least 15 minutes at an eyewash station. This dilutes and washes away the chemical to minimize damage while you seek further medical attention.

35. In a titration experiment, 25.0 mL of 0.1 M NaOH is required to neutralize 20.0 mL of HCl solution. What is the molarity of the HCl solution?

• A. 0.08 M
• B. 0.125 M
• C. 0.2 M
• D. 0.25 M

Explanation: For neutralization, moles of NaOH = moles of HCI. Moles of NaOH = 0.1 mol/L x 0.025 L = 0.0025 mol. Molarity of HCI=moles/volume=0.0025/0.020= 0.125 M.

36. Which piece of apparatus is most suitable for accurately measuring 10.00mL of a liquid in a titration experiment?

• A. Beaker
• B. Measuring cylinder
• C. Pipette
• D. Burette

Explanation: A pipette provides high precision for measuring a fixed volume like 10.00 mL. unlike a beaker or measuring cylinder. A burette is used for variable volumes.

37. In paper chromatography, a compound has an Rf value of 0.4. If the solvent front travels 8.0 cm, how far does the compound travel?

• A. 2.0 cm
• B. 3.2 cm
• C. 4.0 cm
• D. 8.0 cm

Explanation: Rf distance traveled by compound/distance traveled by solvent. Distance= Rf × solvent distance= 0.4 x 8.0 = 3.2 cm.

38. In a calorimetry experiment to determine the enthalpy of combustion of ethanol, a 100 g water sample increases in temperature by 20.0°C. What is the heat absorbed by the water? (Specific heat of water = 4.18 J/g•°C)

• A. 4180 J
• B. 8360 J
• C. 10450 J
• D. 20900 J

Explanation: Heat q=m × c × ∆T = 100 × 4.18 x 20.0= 8360 J.

39. During a filtration experiment, a student uses filter paper to separate a precipitate. Which technique ensures faster filtration?

• A. Using a larger beaker
• B. Folding the filter paper into a fluted shape
• C. Heating the mixture
• D. Adding more solvent

Explanation: Fluted filter paper increases surface area, allowing faster. filtration compared to flat folding. Other options do not directly improve filtration speed.

40. In a spectrophotometric analysis, a solution absorbs 0.602 units at 450 nm. If the path length is 1.0 cm and the molar absorptivity is 1.5 × 10³ L/mol•cm, what is the concentration of the solution?

• A. 4.01 × 10⁻⁴ M
• B. 2.01 × 10⁻³ M
• C. 4.01 × 10⁻³ M
• D. 9.03 × 10⁻⁴ M

Explanation: Beer-Lambert Law: A = ε × c × l. Concentration c = A/(ε × l) = 0.602/(1.5 × 10³ × 1.0) = 4.01 × 10⁻⁴ M.