Video Transcript
Which of the following statements
best describes the process of volatilization gravimetry? (A) The measurement of the change
in mass after reacting a sample to produce a precipitate. (B) The measurement of the change
in mass after removing volatile compounds from a sample. (C) The measurement of the change
in volume after mixing two samples together. (D) The measurement of the change
in concentration after neutralizing a sample.
The term volatilization refers to
evaporating substances. In volatilization gravimetry,
thermal or chemical energy converts some solid molecules in a sample into gaseous
molecules. These substances are volatile,
which means they have low boiling points and can be evaporated from the solid
without a large input of energy.
In the lab, a hydrated salt could
be heated in a crucible with a Bunsen burner to separate water molecules from the
salt. Or a bicarbonate salt, such as
potassium bicarbonate, could be reacted with an acid to separate molecules of carbon
dioxide gas from the salt. In both examples, we could measure
the mass of the solid sample before and after the experiment to determine the change
in mass. In fact, the term gravimetry refers
to measuring mass.
Now we understand that we are
concerned with a change in the mass when we do a volatilization gravimetry
experiment, not a change in volume or concentration. Knowing this allows us to eliminate
answer choices (C) and (D).
We can also eliminate answer choice
(A) because it refers to precipitation gravimetry. Precipitation gravimetry is a mass
analysis method that uses a precipitation reaction to make mass measurements of
substances. On the other hand, volatilization
gravimetry is a mass analysis method that uses thermal or chemical energy to
separate volatile components from a compound or mixture.
In conclusion, the statement that
best describes the process of volatilization gravimetry is answer choice (B): the
measurement of the change in mass after removing volatile compounds from a
sample.
