,1. What is the primary purpose of a buffer in a chemical reaction?
A) To increase the reaction rate
B) To control pH
C) To act as a catalyst
D) To provide color change
Correct Answer: B) To control pH
Rationale: Buffers are used to maintain a constant pH in a
solution, which is crucial for many biochemical reactions that are
sensitive to changes in pH levels.
,3. Which piece of laboratory equipment is used to measure the
volume of liquids with the greatest precision?
A) Beaker
B) Graduated cylinder
C) Volumetric flask
D) Burette
Correct Answer: D) Burette
Rationale: Burettes are designed to deliver precise volumes of
liquid, with graduations that allow for measurements to the nearest
0.1 mL, making them ideal for titrations.
4. What is the molarity of a solution containing 5 moles of solute in
2 liters of solution?
A) 2.5 M
B) 5 M
C) 10 M
D) 7.5 M
Correct Answer: A) 2.5 M
Rationale: Molarity is defined as the number of moles of solute
per liter of solution. Therefore, \( \frac{5 \text{ moles}}{2 \text{
liters}} = 2.5 \text{ M} \).
, 5. When performing a gravimetric analysis, why is it important to
thoroughly dry the precipitate?
A) To ensure accurate weighing
B) To prevent chemical reactions
C) To enhance solubility
D) To change the precipitate's color
Correct Answer: A) To ensure accurate weighing
Rationale: Any moisture in the precipitate can add to its weight,
leading to inaccurate results. Drying removes this variable, allowing
for precise measurement of the precipitate's mass.
6. What is the principle behind chromatography?
A) Precipitation
B) Filtration
C) Phase separation
D) Centrifugation
Correct Answer: C) Phase separation
Rationale: Chromatography separates components of a mixture
based on their different interactions with the stationary and mobile
phases, leading to phase separation.
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