The formality of a solution is defined as the number of formula mass of any solute dissolved in 1 litre of solution. Therefore, there is scarcely any difference between formality and molarity of a solution.

Formula (NaCl) mass of sodium chloride = 23 + 35.5 = 58.5 .

58.5 g NaCl when dissolved in 1000 cm^3 solution becomes 1 formal solution ;

from http://www.chemiasoft.com/chemd/node/25

1.5.1 Molarity and Formality

Both molarity and formality express concentration as moles of solute per liter of solution. There is, however, a subtle difference between molarity and formality. Molarity is the concentration of a particular chemical species in solution. Formality, on the other hand, is a substance’s total concentration in solution without regard to its specific chemical form. There is no difference between a substance’s molarity and formality if it dissolves without dissociating into ions. The molar concentration of a solution of glucose, for example, is the same as its formality.

For substances that ionize in solution, such as NaCl, molarity and formality are different. For example, dissolving 0.1 mol of NaCl in 1 L of water gives a solution containing 0.1 mol of Na+ and 0.1 mol of Cl–. The molarity of NaCl, therefore, is zero since there is essentially no undissociated NaCl in solution. The solution, instead, is 0.1 M in Na+ and 0.1 M in Cl–. The formality of NaCl, however, is 0.1 F because it represents the total amount of NaCl in solution. The rigorous definition of molarity, for better or worse, is largely ignored in the current literature, as it is in this text. When we state that a solution is 0.1 M NaCl we understand it to consist of Na+ and Cl– ions. The unit of formality is used only when it provides a clearer description of solution chemistry.

Molar concentrations are used so frequently that a symbolic notation is often used to simplify its expression in equations and writing. The use of square brackets around a species indicates that we are referring to that species’ molar concentration. Thus, [Na+] is read as the “molar concentration of sodium ions”.

Note that it is the final volume of the solution that is important, not the starting volume of the solvent used. The final volume of the solution might be a bit larger than the volume of the solvent because of the additional volume of the solute. In practice, a solution of known molarity is prepared by weighing an appropriate amount of solute and placing it in a volumetric flask. Enough solvent is added to dissolve the solute, and further solvent is added until an accurately calibrated final volume is reached.

The formality of a solution is defined as the number of formula mass of any solute dissolved in 1 litre of solution. Therefore, there is scarcely any difference between formality and molarity of a solution.

Formula (NaCl) mass of sodium chloride = 23 + 35.5 = 58.5 .

58.5 g NaCl when dissolved in 1000 cm^3 solution becomes 1 formal solution ;

from http://www.chemiasoft.com/chemd/node/25

1.5.1 Molarity and Formality

Both molarity and formality express concentration as moles of solute per liter of solution. There is, however, a subtle difference between molarity and formality. Molarity is the concentration of a particular chemical species in solution. Formality, on the other hand, is a substance’s total concentration in solution without regard to its specific chemical form. There is no difference between a substance’s molarity and formality if it dissolves without dissociating into ions. The molar concentration of a solution of glucose, for example, is the same as its formality.

For substances that ionize in solution, such as NaCl, molarity and formality are different. For example, dissolving 0.1 mol of NaCl in 1 L of water gives a solution containing 0.1 mol of Na+ and 0.1 mol of Cl–. The molarity of NaCl, therefore, is zero since there is essentially no undissociated NaCl in solution. The solution, instead, is 0.1 M in Na+ and 0.1 M in Cl–. The formality of NaCl, however, is 0.1 F because it represents the total amount of NaCl in solution. The rigorous definition of molarity, for better or worse, is largely ignored in the current literature, as it is in this text. When we state that a solution is 0.1 M NaCl we understand it to consist of Na+ and Cl– ions. The unit of formality is used only when it provides a clearer description of solution chemistry.

Molar concentrations are used so frequently that a symbolic notation is often used to simplify its expression in equations and writing. The use of square brackets around a species indicates that we are referring to that species’ molar concentration. Thus, [Na+] is read as the “molar concentration of sodium ions”.

Note that it is the final volume of the solution that is important, not the starting volume of the solvent used. The final volume of the solution might be a bit larger than the volume of the solvent because of the additional volume of the solute. In practice, a solution of known molarity is prepared by weighing an appropriate amount of solute and placing it in a volumetric flask. Enough solvent is added to dissolve the solute, and further solvent is added until an accurately calibrated final volume is reached.

formality is a formula weight in one litre of solution, normality is no. Of moles of solute in one of the solvent. Molality is no of moles of solute in thousand gram of solvent

Molality is the number of moles of solute dissolved in one kilogram of solvent.

Molarity is the number of moles of a solute dissolved in a liter of solution.

Formality of a solution is defined as the number of formula mass dissolved in a liter of solution.

Equivalent weight = molar mass/(H+ per mole)

Equivalent = mass of compound / Equivalent weight

Normality = (equivalents of X)/Liter

1. Molarity. The molarity of a solution is the number of moles of the solute contained in one liter of the solution.

 Molarity = ( number of moles of solute )/Liter of solution

2. Formality. The formality of a solution is the number of gram-formula weights of the solute contained in one liter of the solution. 

Formality = ( number of gram of solute/gram-formula weights of the solute)/Liter of solution

3. Normality. The normality of a solution is the number of gram-equivalent weights of the solute contained in one liter of the solution.

Normality = (equivalents of X)/Liter of solution

Are different measurement units of concentration, each of which has its own definition

There appears to be an awful lot of confusion about what formality actually refers to in text books! To be honest I had never heard of it!