lab2zinc oxide 2024-2025.pdf

Residual Titration Method Lecturer Luma Amer Department of Pharmaceutical Chemistry/Collage of pharmacy 3rdstage: 2ndlab. Inorganic Pharmaceutical Chemistry Practical Experiment 2 Residual Titration Method Assay of Zinc Oxide ...

Residual Titration Method Lecturer Luma Amer Department of Pharmaceutical Chemistry/Collage of pharmacy 3rdstage: 2ndlab. Inorganic Pharmaceutical Chemistry Practical Experiment 2 Residual Titration Method Assay of Zinc Oxide  Residual Titration A process in which the excess of standard solution used to react with an analyte is determined by titration with second standard solution.  Aim of the Experiment Aim: The aim of the experiment is to determine the amount of zinc oxide in a pharmaceutical preparation. Introduction Zinc oxide, ZnO, is a white powder that is insoluble in water. It is an additive in many industrial uses including food as a source of zinc. Zinc oxide is a topical agent. A mixture of zinc oxide with 0.5% iron(III) oxide is called calamine. The latter is used as lotion. Zinc oxide can be used in ointments and creams to protect against sunburn and other damage to the skin caused by UV.  Principle Equation: ZnO + H2SO4 → ZnSO4 + H2O H2SO4 + 2 NaOH → Na2SO4 +2 H2O When zinc oxide is dissolved with an excess sulphuric acid, a neutralization reaction takes place. The amount of acid remaining is titrated with a standard solution of sodium hydroxide. Materials Required Zinc oxide: unknown g Sulphuric acid: 1N Sodium hydroxide: 1N Ammonium chloride: 2.5g Methyl orange  Procedure: 1- Using sensitive balance NO.1, Weigh accurately about 0.5 g of Zno in a suitable beaker. 2- Using sensitive balance NO.1, Weigh 2.5g of NH4Cl, in the same baker. 3- Dissolve with 30ml of 1N H2SO4 solution in fume hood NO.1 and stir the mixture. Notice the formation of a turbid solution. 4- Gently heat the resulting mixture using heater NO. 1until a clear solution is obtained. 5-Add two drop of methyl orange solution as indicator. (Fume hood NO.1) 6- Fill the burette with 1 N NaOH, (Fume hood NO.1) and start the titration procedure. 8- complete your calculations.  Procedure (unk.): 1- Dissolve the smple with 50ml of 1N H2SO4 solution and stir the mixture. Notice the formation of a turbid solution. 2- Gently heat the resulting mixture using hot plate magnetic stirrer until a clear solution is obtained. 3- Transfer 10 ml from previous solution to a conical flask. 4-Add two drop of methyl orange solution as indicator. 5- Fill the burette with 1 N NaOH, and start the titration procedure. 6- Repeat the previous titration process. 7-calculate the Wt. practical for the sample ZnO if you know that: The molar mass of ZnO is 81.408 g/mol  1N NaOH g ZnO +2.5 g NH4Cl +50 ml 1N H2SO4 heating + 2 drop m.o.  m.o. Pink yellow pH=3.2 pH= 4.4  calculations ZnO + H2SO4 → ZnSO4 + H2O H2SO4 (excess)+ 2 NaOH → Na2SO4 +2 H2O mEq. of NaOH = mEq. of H2SO4 + mEq. of ZnO mEq. of ZnO = mEq. of H2SO4 - mEq. of NaOH mEq. of ZnO = N H2SO4 * V H2SO4 - N NaOH *( V NaOH * 50/10) = mEq. Of ZnO Wt. of ZnO mg = mEq. of ZnO * Eq.Wt. of ZnO Wt. of ZnO mg = mg / 1000 = g Wt.% = wt. practical / wt. Theoretical *100 Assume wt. Theoretical = 0.5 g ZnO = 500 mg Calculations (2) % ZnO = ( Vtot–Vrem) x meq.wt x100 / wt of sampl Where V tot = Total volume of H2SO4 V rem = volume of H2SO4 react with NaOH Safety of zinc oxide Potential Acute Health Effects: Hazardous in case of inhalation. Slightly hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion  Safety of ammonium chloride chemical dangers decomposes on heating. This produces toxic and irritating fumes (nitrogen oxides, ammonia and hydrogen chloride). Hazardous in case of eye contact (irritant). Slightly hazardous in case of skin contact (irritant, sensitizer), of ingestion, of inhalation Safety of sodium hydroxide Very hazardous in case of skin contact (corrosive, irritant, permeator), of eye contact (irritant, corrosive), of ingestion,of inhalation. The amount of tissue damage depends on length of contact. Eye contact can result in corneal damage orblindness. Skin contact can produce inflammation and blistering. Inhalation of dust will produce irritation to gastro-intestinal or respiratory tract, characterized by burning, sneezing and coughing.