States of Matter Test - 18

No. of moles in five litres of gas at $$STP$$ $$=$$$$5/22.4 \:mol$$ 

The expression $$\displaystyle 10\times \left( 6.022\times { 10 }^{ 23 } \right)/ 55.9$$ is equal to the number of iron (Fe) atoms present in 10.0 g Fe.
The atomic mass of Fe is 55.9 g/mol.
The mass of Fe is 10.0 g. Mass is divided with atomic mass to obtain number of moles.
The number of moles of Fe $$ =  \dfrac {10.0}{55.9}$$ moles.
The number of moles is multiplied with avogadro's number to obtain the number of Fe atoms.
The number of Fe atoms  $$ =  \dfrac {10.0}{55.9} \times 6.023 \times 10^{23}$$.

The pressure of the gas  is equal to the sum of the atmospheric pressure and the pressure due to the difference in the mercury level. The pressure of the gas $$= 760 + 80 = 840 \:mm \:Hg$$.

Very high densities, very high pressures, very low volumes and very low temperatures are considered 'non-ideal'.
Moderate densities, moderate pressures, moderate volumes and moderate temperatures are considered 'ideal'.

Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules". For a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.

Kinetic model of gases, five assumptions are made:

1. Gases are made up of particles with no defined volume but with a defined mass. In other words their volume is miniscule compared to the distance between themselves and other molecules.
2. Gas particles undergo no intermolecular attractions or repulsions. This assumption implies that the particles possess no potential energy and thus their total energy is simply equal to their kinetic energies.
3. Gas particles are in continuous, random motion.
4. Collisions between gas particles are completely elastic. In other words, there is no net loss or gain of kinetic energy when particles collide.
5. The average kinetic energy is the same for all gases at a given temperature, regardless of the identity of the gas. Furthermore, this kinetic energy is proportional to the absolute temperature of the gas.

Dalton's law (also called Dalton's law of partial pressures) states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. 

The ideal of perfume making is that to make it diffuse faster such that its fragrances should reach nearby things or persons in a short time. So, the material used in perfume making will diffuse faster than others.