Question

What is the formula for calculating the pressure of a gas?

Answer 1

Hint : We can use the equation for ideal gas given by the ideal gas law and then using the given quantities of temperature, pressure and density which relationship amongst them is constant throughout.

Complete Step By Step Answer:
The given pressure, temperature and density are p, T and d respectively. Let its mass be m and molecular mass be M. According to the ideal gas law, the equation for ideal gas is given as:
$PV=nRT$
It can be rewritten as; $P=\dfrac{nRT}{V}.$
Where, p is the pressure, n is the number of moles of gas, R is universal gas constant and T is the temperature. Number of moles (n) is equal to the mass of the gas (m) divided by its molecular mass (M)
It's important to pay attention to the units, however. In strict SI units (highly recommended), expressed in moles, R is the universal gas constant $8.314J/molK$ T is the temperature in Kelvins, and the volume V is in ${{m}^{3}}.$ The resulting pressure P will be in Pa. The other common set of units is where V is in liters (L) and $R=0.082054L-atm/mol-K$
Example:
$0.25$ mol of helium gas confined to a $6L$ vessel at $250K$ will have a pressure equal to
$P=\dfrac{nRT}{V}=\dfrac{\left( 0.25mol \right)\left( 0.082054 \right)\left( 250K \right)}{6L}=0.855atm.$

Note :
We have to see what the quantities are given and what replacements need to be done so that we can get desired quantities in the equation. We found a constant relationship because from the question we can say that both the states of these physical quantities are equal and this will only be possible when their relationship would be constant.