Question

Model 1 shows 0.200 moles of NaCl in the flask; however, moles cannot be measured directly in the lab. How must the solid be measured instead?

A) By its volume

B) By its mass

C) By its temperature

D) By its density

Answer 1

In the lab, solid substances like NaCl are measured by their mass, which is determined using a balance and the substance's molar mass, allowing for the precise calculation needed for experiments.

Step-by-step explanation:

When dealing with solid substances in the laboratory, like NaCl (sodium chloride), chemists must measure them indirectly because moles cannot be directly measured. Instead, the solid must be measured by its mass, using a balance.

Mass is a more reliable measurement as it is not affected by temperature, unlike volume that can vary with changes in temperature. To determine the amount of NaCl needed for a particular experiment, the molar mass of NaCl must be known, which can be found on the periodic table or chemical databases.

Once the molar mass is identified, dimensional analysis is used to calculate the mass that corresponds to the desired number of moles.