American Chemical Society (ACS) Chemistry Practice Exam

The ideal gas constant, R, has different values depending on the units used in calculations. When dealing with meters per mole Kelvin, the appropriate value of R is 8.3145 m³/mol K. This value is derived from the ideal gas law, where pressure, volume, temperature, and amount of substance are related. In this context, the volume is expressed in cubic meters (m³), and since R reflects the relationship between these variables in the ideal gas law, using m³ ensures the correct dimensional analysis when considering the unit of pressure in pascals (Pa). The significant aspect of this value is that it allows for compatibility with the SI units of measurement commonly used in scientific contexts, connecting temperature (in Kelvin), amount of substance (in moles), and volume (in cubic meters). Alternative options provided do not align with the requirement of being expressed in meters per mole Kelvin. For instance, the value associated with liters signifies a different volumetric measure. Thus, the option representing 8.3145 m³/mol K is the correct answer for this context.