No, the ideal gas equation, also known as the ideal gas law, cannot be used if not all the variables (temperature, pressure, or volume) are known. The ideal gas equation is expressed as:
PV = nRT
where: P = pressure of the gas V = volume of the gas n = number of moles of gas R = ideal gas constant T = temperature of the gas (in Kelvin)
The equation relates the pressure, volume, temperature, and amount of gas in a closed system. To use the ideal gas equation, you need to know the values of three of the variables to solve for the fourth.
If not all the variables are known, you can't directly use the ideal gas equation to calculate the unknown variable. However, if you have additional information or data, such as the relationship between two variables (e.g., through another equation or experimental data), you may be able to determine the unknown variable using that information along with the ideal gas equation.