Kinetic theory of gases

The ideal gas law summarizes certain physical properties of gases at low pressure.The kinetic theory of gases  provides a microscopic understanding of Boyle's law and also a microscopic mechanical definition of temperature as a measure of the average kinetic energy of the molecule in a gas.

The underlying assumption of the kinetic theory of gases are simple:

1. A pure gas consists of a large number of identical molecules separated by distance that are compared with their size.

2. The gas molecules are constantly moving in a random directions with a distribution of speed.

3. The molecules exert no forces on one another between collisions, so between collisions they move in straight lines with constant velocity.

4. The collisions of molecules with the walls of the container are elastic, no energy is lost during a collision.

  

Ideal gas equation

It can be contructed by combining Charle’s, Boyle’s and Avagadro’s laws.

The ideal gas equation   has the following form:

PV = nRT

The P presents the pressure in atmosphere(atm), V represents volume in litres(L). the n represents the moles of gas, the T represents the temperature in Kelvin(K) and R represents the ideal gas constant, which is 0.0821atm/K mol.

Molality and Normality

 Molality 
Many physical properties are related to solution concentration expressed as Molality m, the number of moles of solute dissolved in one kilogram of solvent. The defining equation is:

                            mol solute
                  m  =   ------------
                            kg solvent

If a solution contain 0.755 mole of acetic acid per kilogram of water, we identify it as 0.755 m

CH₃COOH. In a calculation setup, we would write "0.755 mol CH₃COOH/kg H₂O".

 

Normality
It is defined a one gram equivalent of a solute per litre of solution. The definition of a gram equivalent varies depending upon the type of chemical reaction. It is critical to note that normality measures a single ion which takes part in an overall solute. For example , one could determine the normality of hydroxide or sodium in an aqueous solution of sodium hydroxide.But the normality of sodium hydroxide has no meaning. However it is often used to describe solutions of acids or bases.So in these cases Normality refers to H⁺ or OH^- 


In acid base chemistry, Normality is used to express the concentration protons or hydroxide ions in a solution. In redox solutions, normality measures the quantity of oxidizing or reducing agent that can accept or furnish one mole of electrons.     



    

    

Kelvin scale of temperature

About 200 years ago , It was noticed that sample of gas that is cooled decreases in volume in a regular way. If the volume were to continue to decrease in the same way  it would become zero at about -273.15 degree Centigrade. This temperature is the minimum temperature, the absolute zero. The new temperature scale as devised by Lord Kelvin which is known as Kelvin scale. it is defined in such a way so as to permit law of Thermodynamics.

The absolute zero is taken to be 0 K(degree kelvin) and the triple point of water is taken as 273.16K. Triple point of water is the pure liquid water , ice , and water vapor in equilibrium.Thus boiling point of water at one atmosphere is 373.15K and freezing point of water at one atmosphere is 273.16K.

Below is the formula defining the relationship of Kelvin temperature a well as Celcius as below:

                                                        K = C + 273.16

K - > Kelvin temperature
C -> Celsius temperature                    

   

Molarity & Molar solution

Molarity is defined as the number of moles of solute dissolved in 1 litre of solution: this is

                      Molarity = number of moles of solute 
                                             L solution

Molarity has a unit moles per litre (Mol L^-1). By convention , we use square brackets[] to represent molarity.

Determine how many grams of Na⁺ would be present in 1L of sea water.

                                     1.06% = 1.06 g Na⁺  so to find how much in 1L multiply by 10

                                                     100mL

                                

                                      1.06% = 10.6 g Na⁺

                                                                       ^1000mL

Determine how any moles in are present in 10.6 g of Na⁺

                                  Moles Na⁺  = 10.6 g            =    0.46 moles.

                                                         23.0 g/mol

Thus the seawater has the molarity of Na+ of 0.46M.