Free Experimental Techniques in Chemistry MCQs with Answers

41. Which of the following is a common error in titration that leads to an overestimation of the analyte concentration?

• A. Rinsing the burette with distilled water instead of the titrant
• B. Reading the burette at the top of the meniscus
• C. Adding too much indicator
• D. Using a dry conical flask

Explanation: Rinsing with water dilutes the titrant, requiring more volume to reach the endpoint, thus overestimating the analyte concentration.

42. In a recrystallization experiment, why is a minimum amount of hot solvent used to dissolve the crude product?

• A. To increase the yield of crystals
• B. To prevent decomposition of the compound
• C. To ensure rapid cooling
• D. To maximize solubility of impurities

Explanation: Using a minimum amount of hot solvent keeps the solution saturated, maximizing crystal yield upon cooling while impurities remain dissolved.

43. In an experiment to determine the rate of reaction between marble chips (CaCO₃) and HCl, the volume of CO₂ produced is measured. Which factor would NOT affect the rate of CO₂ production?

• A. Concentration of HCl
• B. Surface area of marble chips
• C. Temperature of the reaction
• D. Volume of the reaction flask

Explanation: The flask's volume does not affect the reaction rate, which depends on concentration, surface area, and temperature.

44. In a distillation to separate two liquids with boiling points of 80°C and 100°C, why are anti-bumping granules added?

• A. To increase the boiling point
• B. To prevent superheating and ensure smooth boiling
• C. To enhance the separation efficiency
• D. To reduce the distillation time

Explanation: Anti-bumping granules provide nucleation sites, preventing superheating and ensuring smooth boiling during distillation.

45. The diagram shows a conical flask connected to a funnel fitted with filter paper. Which piece of apparatus ensures faster separation of the filtrate under reduced pressure?

• A. Buchner funnel
• B. Buchner flask connected to suction
• C. Rubber tubing
• D. Porous plate

Explanation: The Buchner funnel, when used with a vacuum flask, allows rapid filtration under suction.

46. A filtration process could be very time consuming if it were not aided by a gentle suction, which is developed:

• A. If the stem of the funnel is large so that it dips into the filtrate
• B. If the paper covers the funnel up to its circumference
• C. If the paper fits tightly
• D. If the paper has got small sized pores in it

Explanation: During filtration, a tight-fitting filter paper prevents the liquid from bypassing the paper around the edges. This ensures all the liquid passes through the paper, maintaining suction efficiency.A proper fit reduces filtration time and prevents loss of solid.

47. How do you properly dispose of chemicals not needed in the experiment?

• 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. Dispose of chemicals in proper places and follow posted procedures without returning them to their original containers.

Explanation: Dispose of chemicals in proper places and follow posted procedures without returning them to their original containers. Unused or excess chemicals should not be returned to stock bottles to avoid contamination. They must be disposed of according to lab safety guidelines in designated waste containers. This ensures safety and prevents chemical reactions or accidents.

48. In the experimental setup shown, the beaker contains a clear liquid labeled X obtained after filtration. Which of the following correctly identifies the substance labeled X?

• A. Residue
• B. Filtrate
• C. Precipitate
• D. Suspension

Explanation: The clear liquid that passes through filter paper is the filtrate, containing the dissolved components.

49. In the crystallization setup shown, the solution has been gently heated to reach the point of saturation. What should be the next correct step to obtain pure crystals?

• A. Continue boiling till dryness
• B. Add more solute
• C. Cool solution slowly
• D. Add cold water

Explanation: Once saturation is reached, gentle cooling allows crystals to form gradually with high purity.

50. During the sublimation process illustrated, vapors condense on the cold surface labeled X. Which substance is most likely collected at this point?

• A. Sand
• B. Water
• C. Ammonium chloride
• D. Sodium chloride

Explanation: Ammonium chloride sublimes on heating and re-solidifies on a cold surface.