$\frac{\rho_{1} V _{1}}{ T _{1}}=\frac{\rho_{2} V _{2}}{ T _{2}}$ $\Rightarrow \frac{10^{-6} \times 1000}{298}=\frac{760 \times V _{2}}{273}$ $V _{2}=1.2 \times 10^{-6} cc ($ at $\quad STP )$ No. of molecules $=\frac{6.02 \times 10^{23}}{22400} \times 1.2 \times 10^{-6}$ $=3.2 \times 10^{13}$
The gas laws were developed at the end of the 18th century, when scientists began to realize that relationships between pressure, volume and temperature of a sample of gas could be obtained which would hold to approximation for all gases.
The five gas laws are:
Boyle’s Law, which provides a relationship between the pressure and the volume of a gas.
Charles’s Law, which provides a relationship between the volume occupied by a gas and the absolute temperature.
Gay-Lussac’s Law, which provides a relationship between the pressure exerted by a gas on the walls of its container and the absolute temperature associated with the gas.
Avogadro’s Law, which provides a relationship between the volume occupied by a gas and the amount of gaseous substance.
The Combined Gas Law (or the Ideal Gas Law), which can be obtained by combining the four laws listed above.