Experiment No. 1 Preparation and standardization of 0.1N hydrochloric

Experiment No. 1 Preparation and standardization of 0.1N hydrochloric acid (HCl) by using standard sodium carbonate (Na2CO3)

Hydrochloric acid (HCl) is not standard substance; therefore it must be standardized by using standard sodium carbonate (Na2CO3). Na2CO3 2 HCl 2 NaCl H2CO3 2 NaCl CO2 H2O

Preparation of solutions 1- Prepare 0.1N Na2CO3 in 250mL of distilled water Na2CO3 is a solid substance. Wt Wt N eq.wt V (ml) eq.wt F.wt of Na2CO3 2 1 1000 0.1 53 250 1000 eq.wt eq.wt 2 23 1 12 3 16 2 106 2 53 g/mol Wt 1.325 g Dissolve 1.325 g Na2CO3 in 250 ml of distilled water to obtain 0.1N Na2CO3.

2- Prepare 0.1N HCl in 250mL of distilled water HCl is a liquid substance. Sp.gr 1.19 %HCl 37% N Sp.gr % 1000 eq.wt eq.wt 1.19 N N 12 eq/L 36.5 37 100 1000 eq.wt F.wt of HCl 1 1 1 1 35.5 1 eq.wt 36.5 g/mol

no. of milliequivalence before dilution no. of milliequivalence after dilution (N1 V1) conc. (N2 V2) dilu. 12 V1 V1 0.1 250 0.1 250 12 2.08 ml 2.1 ml Take 2.1 ml of concentrated HCl with a pipet, and dilute to 250 ml with distilled water in a 250ml-volumetric flask to obtain approximately 0.1 N HCl.

Procedure: 10ml of HCl (0.1N) 0.1 N Na 2CO3 solution 2-3 drops of methyl orange 10 ml of HCl solution 2 drops of methyl orange The Colour changed from Red - to - yelow (1) (2) (3)

Calculation At the equivalence point no. of milliequivalence of Na2CO3 no. of milliequivalence of HCl (N1 V1) Na2CO3 (N2 V2) HCl 0.1 Vaverage N2 N2 10 0.1 Vaverage 10 ( ) eq/L HCl