Which of the following is NOT a variable in the ideal gas law equation PV = nRT?

• A. T (temperature)
• B. P (pressure)
• C. V (volume)
• D. R (the gas constant)

Answer: (D)

Verified step by step guidance

1. Recall the ideal gas law equation: \(PV = nRT\), where \(P\) is pressure, \(V\) is volume, \(n\) is the number of moles, \(R\) is the gas constant, and \(T\) is temperature.
2. Identify which symbols represent variables that can change during an experiment: \(P\), \(V\), \(n\), and \(T\) are variables because their values can vary depending on the conditions.
3. Recognize that \(R\) is the gas constant, a fixed value that does not change regardless of the gas or conditions; it is a proportionality constant.
4. Understand that the question asks which is NOT a variable, so the answer must be the symbol representing a constant rather than a changing quantity.
5. Conclude that \(R\) (the gas constant) is NOT a variable in the ideal gas law equation.