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My assignment is as follows:
A sample of air is trapped in a container at $\pu{16.2 psi}$. If the initial temperature is increased from $\pu{10 ^\circ C}$ to $\pu{32 ^\circ C}$, what is the final pressure?
I am really confused as to what $\pu{psi}$ is and how am I supposed to convert it to figure out the final pressure.
In the given experiment, there is no indication that the volume of the container changes and/or a reaction takes place. Both the volume and the amount of substance can therefore assumed to be constant.
Let's assume that the enclosed air can be treated as an ideal gas.
Under these conditions, the pressure is proportional to the absolute temperature (in Kelvin): \begin{align} p &\propto T & \frac{p_1}{p_2} &= \frac{T_1}{T_2} \end{align}
This relation is known as Amonton's Law.
I am really confused as to what psi is and how am I supposed to convert it to figure out the final pressure.
Using the equation above, you would only have to convert the temperatures to Kelvin and could give the final pressure as $\pu{psi}$ too.
If you insist on conversion to Pascal ($\pu{Pa}$) as your favourite SI unit for pressure, remember that a pressure is defined as a force acting on a surface (area): $$\pu{1 Pa} = \pu{1 N//m^2} = \pu{1 kg//m s^2}$$
The $\pu{psi}$ is a still rather common unit and it stands for pounds per square inch.
This is double weird, since both the force and the area are expressed in non-SI units.
Note that the pound is not the German Pfund ($= \pu{0.500 kg}$), but the angloamerican pound with $\pu{1 lb} = \pu{0.453 kg}$.
The area part in $\pu{psi}$ is given in square inches with $\pu{1 in} = \pu{0.0254 m}$.
In summary, $\pu{1 psi} \approx \pu{6895 Pa}$.
