Chapter- 4 : Reagents (solution) used in clinical laboratories

Quantitative expressions…..

• Normal solution (Normality)
• - Normality is defined as the number of equivalent of solutes that are present in one liter of solution. If 1 gm equivalent H2SO4 is dissolved in one liter of solution it is called Normal solution of H2SO4 or 1N H2SO4.
• NB. One equivalent of substance is its equivalent weight expressed in grams.
• Normality = Actual Mass in grams
• Equivalent weight x vol. in liter
• Weight to be dissolved = equivalent weight x vol. in L x Normality.

Quantitative expressions…..

• Example-1 what is the normality of KOH. If 5.6gm KOH is dissolved in 1 liter
• of solution?
• Solution
• Actual mass = 5.6gm
• Volume = 1 lit
• N= Actual Mass in gram
• Equ. Wt x vol in lit
• = 5.6gm = 0.1NKOH
• 56 x 1

Quantitative expressions…..

• Example-2. Prepare 0.2N NaOH solution in 1 liter.
• V= 1 liter
• Actual mass=?
• Normality = 0.2N
• Equiv. wt= 40
• N= Actual mass in gram
• Equ. Wt x vol in liter
• 0.2 = x
• 40x1
• Actual mass = 8gm
• There for 8gm is dissolved in a liter of solution to give 0.2N NaOH.

Quantitative expressions…..

• Molality(m) =

• moles of solute

• mass of solvent (kg)

• Example : What is the molality of a 5.86 M ethanol (C2H5OH) solution whose density is 0.927 g/mL?

Quantitative expressions…..

• Assume 1 L of solution:
• 5.86 moles ethanol = 270 g ethanol
• 927 g of solution (1000 mL x 0.927 g/mL)

• mass of solvent = mass of solution – mass of solute

• = 927 g – 270 g = 657 g = 0.657 kg

• m =

• moles of solute

• mass of solvent (kg)

• =

• 5.86 moles C2H5OH

• 0.657 kg solvent

• = 8.92 m