Question

A gas has a density of \[\text{2}\text{.68g/L }\!\!~\!\!\text{ }\] at STP. Identify the gas.
A \[\text{N}{{\text{O}}_{\text{2}}}\]​
B Kr
C COS
D \[\text{S}{{\text{O}}_{\text{2}}}\]

Answer 1

Hint: Standard sets of settings for experimental measurements are produced at standard temperatures and pressures (STP), allowing comparisons to be made between various sets of data. These conditions are 0 degrees Celsius and 1 atmosphere (atm) of pressure. The volume of 1 mol of an ideal gas is 22.4 L.

Complete step-by-step answer:The density of a substance indicates how dense it is in a given area. Mass per unit volume is the definition of a material's density. In essence, density is a measurement of how closely stuff is packed. It is a particular physical characteristic of a specific thing. The relationship between a substance's mass and the volume it occupies is known as its density.
The mathematical formula of density is shown below.
$\begin{array}{*{35}{l}}
   Density=\frac{Mass}{Volume} \\
\end{array}$
$\begin{array}{*{35}{l}}
   \rho =\frac{m}{v} \\
\end{array}$
At STP, volume of 1 mole of ideal gas = 22.4L
\[\therefore \] Mass = Density \[\times \] Volume
\[~\text{ }~\text{ }~\text{ }~\text{ }~\text{ }~\text{ }~=2.68\times 22.4\]
\[~\text{ }~\text{ }~\text{ }~\text{ }~\text{ }~\text{ }~\simeq 60g\]
Now, The molar mass of COS is calculated as shown below
Molar mass of COS=12 g/mol +16 g/mol +32 g/mol =60 g/mol.
Therefore, the COS has a density of \[\text{2}\text{.68g/L }\!\!~\!\!\text{ }\] at STP.

Option ‘C’ is correct

Note:Avogadro’s law is used to calculator molar volume of ideal gas which states that “under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules”. For one mole of gas at STP this value of 22.4 L.