CHEM 121 LAB REPORTS 3 PROFESSIONAL
EXAMPREP 2026 TESTED QUESTIONS AND
SOLUTIONS FULL REVIEW GRADED A+
◉ Which described method is NOT an example of a physical
separation? Answer: Adding a solution that reacts with only one
component of the mixture to create a precipitate
◉ What is an iron ring used for? Answer: Supporting a beaker on a
piece of wire mesh. Suspending a funnel. Holding a crucible placed
in a clay triangle.
◉ When using a clamp to secure a flask to a ring stand, begin by
choosing a ring stand and clamp that are appropriately sized for the
_______. Position the clamp directly
_______ the base of the ring stand. Turn the knobs of the clamp,
making sure not to
_______the clamp around any glassware. Answer: glassware, above,
overtighten
◉ Barium can be analyzed by precipitating it as BaSO4 and
determining the mass of the precipitate. When a 0.269-g sample of a
barium compound was treated with excess H2SO4, 0.0891 g of
, BaSO4 formed. What percentage of barium is in the compound?
Answer: 19.5%
◉ A series of measurements in the lab led to an experimental result
of 32.9 mL, with a calculated standard deviation of 0.3 mL. What is
the standard way to report this result? Answer: 32.9 ± 0.3 mL
◉ What percentage of sodium is in pure table salt? Include two
decimal places in your answer. Answer: 39.34%
◉ Suppose a student repeats a measurement two times and then
calculates the standard deviation. Because the standard deviation is
small, the student reports that their experiment was extremely
precise.
Is the student's conclusion appropriate? Answer: No, because there
were not enough measurements to use standard deviation.
◉ In a precipitation reaction, what symbol identifies the precipitate
product? Answer: (s)
◉ When describing the uncertainty of a measurement, the term
_______refers to the closeness between a measurement and its
accepted value, whereas the term ______ refers to the closeness
among a set of measurements. Answer: accuracy, precision
EXAMPREP 2026 TESTED QUESTIONS AND
SOLUTIONS FULL REVIEW GRADED A+
◉ Which described method is NOT an example of a physical
separation? Answer: Adding a solution that reacts with only one
component of the mixture to create a precipitate
◉ What is an iron ring used for? Answer: Supporting a beaker on a
piece of wire mesh. Suspending a funnel. Holding a crucible placed
in a clay triangle.
◉ When using a clamp to secure a flask to a ring stand, begin by
choosing a ring stand and clamp that are appropriately sized for the
_______. Position the clamp directly
_______ the base of the ring stand. Turn the knobs of the clamp,
making sure not to
_______the clamp around any glassware. Answer: glassware, above,
overtighten
◉ Barium can be analyzed by precipitating it as BaSO4 and
determining the mass of the precipitate. When a 0.269-g sample of a
barium compound was treated with excess H2SO4, 0.0891 g of
, BaSO4 formed. What percentage of barium is in the compound?
Answer: 19.5%
◉ A series of measurements in the lab led to an experimental result
of 32.9 mL, with a calculated standard deviation of 0.3 mL. What is
the standard way to report this result? Answer: 32.9 ± 0.3 mL
◉ What percentage of sodium is in pure table salt? Include two
decimal places in your answer. Answer: 39.34%
◉ Suppose a student repeats a measurement two times and then
calculates the standard deviation. Because the standard deviation is
small, the student reports that their experiment was extremely
precise.
Is the student's conclusion appropriate? Answer: No, because there
were not enough measurements to use standard deviation.
◉ In a precipitation reaction, what symbol identifies the precipitate
product? Answer: (s)
◉ When describing the uncertainty of a measurement, the term
_______refers to the closeness between a measurement and its
accepted value, whereas the term ______ refers to the closeness
among a set of measurements. Answer: accuracy, precision
