Analysis of Acid by Titration with Sodium Hydroxide

Stephanie Thao chemical science 1151 Laboratory Analysis of stifling by titration with sodium hydroxide Ms. Hoang November 2012 Introduction The purpose of this taste is to demonstrate an example of how to restrict the unappreciated metre of hydrochloric sour by titration with a base (sodium hydroxide). Titration is a common research lab method of quantitative chemical substance analysis that is use to determine the unknown preoccupancy of an identified analyte (wekipedia). The stolon step will be measuring and combining water and vitriolic (Hydrochloric astringent).An exponent anthocyanin will be added to the antecedent to change the assumption to knap. Anthocyanin is a water-soluble vacuolar pigment that may come along red, purple, or blue dep shoemakers lasting on the pH (Wikipedia). This beg polish acts as a pH megabyte and will show a change in garble to represent a change in the pH. As the base (sodium hydroxide) is added, the solution will then change c olor (this is referred to as the stoichiometric end shoot for). This color change represents the increase of pH, as well as showing that the moles of the acidulous in the solution are equal to the moles of the base ( check over of alchemy lab manual).Using a dilution equivalence of M1xV1=M2xV2, the denseness of the hydrochloric acid merchant ship be approximated. M1=NaOH( thou), V1=NaOH(volume), M2=HCl( molar concentration), V2=HCl(volume). Procedure Instructions for laboratory were found on page 91 of reexamine of Chemistry lab manual. All calculations were rounded collide with by 2 denary places for accuracy. Preparation of the exponent required a combination of 50 grams of uprise with 50ml of ethanol and 20mL of DI water to raise the anthocyanin index finger. This procedure was finished by the instructor and the anthocyanin indicator (cabbage extract) was provided.Then 10mL of hydrochloric acid and 20mL in of deionized water were measured in a graduated cylinder an d combined into an Erlenmeyer flask. pipette 5 to 10 drops of anthocyanin indicator was added to the solution in Erlenmeyer flask until the solution change to a pink color. Then the solution was titrated with sodium hydroxide until the solution changed color from pink to blue. The titration of the acid was repeated in three trials. All data and calculations were recorded. Data Tables resolving Table Acid Bottle Code 9 running 1 Trial 2 Trial 3 Final buret reading acid (mL) 9. 1 9. 2 10. 10 Volume of acid utilise (mL) 9. 9. 2 10. 10 Final buret reading NaOH (mL) 26. 30 44. 70 45. 50 initial buret reading NaOH (mL) 7. 91 26. 30 26. 50 Volume of NaOH (mL) 18. 39 18. 40 19. 00 Concentration of NaOH (M) 0. 1 0. 1 0. 1 Molarity of the acid (HCl) 0. 202M 0. 199M 0. 182M balance of volume of NaOH used (mL) to volume of acid used (mL) Calculations As previously express in introduction, verbalism M1xV1=M2xV2 found on page 93 of Survey of Chemistry laboratory manual was used to e stimate the concentration of hydrochloric acid (HCl). Trial 1 M1 = 0. 1 (NaOH) V1 = 18. 39mL (NaOH) M2= inscrutable (HCl) V2=9. mL (HCl) 0. 1 x 18. 39 = M2 x 9. 1 1. 839/9. 1 = M2 M2 = 0. 202M Trial 2 M1 = 0. 1 (NaOH) V1 = 18. 40mL (NaOH) M2= mysterious (HCl) V2=9. 2mL (HCl) 0. 1 x 18. 40 = M2 x 9. 2 1. 839/9. 2 = M2 M2 = 0. 199M Trial 3 M1 = 0. 1 (NaOH) V1 = 19. 00mL (NaOH) M2= hidden (HCl) V2=10. 10mL (HCl) 0. 1 x 18. 39=M2 x 10. 10 1. 839/10. 10 = M2 M2 = 0. 182M Average of acid 0. 202 + 0. 199 + 0. 182/3 = 0. 194M = M average Discussion and neighboringdown This lab was successful in the proper color change needed to represent an end wind when acid (hydrochloric acid) and indicator anthocyanin is titrated with a base (sodium hydroxide).As stated in the lab manual anthocyanin will go from a color of pink to blue, a pH of seven to eight, where the blue is an indication that acid has been modify by the base (Survey of Chemistry lab manual). During this audition after adding eno ugh sodium hydroxide to the indicator solution the solution changed color to blue, an indication of the stoichiometric end point. All three trials showed the proper color change. This proved that the color change indicated that the pH train had changed in solution and the amount of base added is chemically equivalent to the acid in the flask.The formula M1xV1=M2xV2 was used to calculate the unknown concentration of hydrochloric acid. The results from the trials showed that the concentration of hydrochloric acid was 0. 2M. The concentration of the two acids should be relatively close in order to cancel each different out. It was complicated to compare the two concentrations since the given molarity of sodium hydroxide is in the one decimal place holder, whereas the calculated concentration for hydrochloric acid is in a two decimal place. From the lab it can be concluded that pH indicators can be an imprecise method to calculate the concentration of an unknown concentration.Critical Thinking Questions 1. Trial 1 M1 = 0. 1 (NaOH) V1 = 18. 39mL (NaOH) M2=Unknown (HCl) V2=9. 1mL (HCl) 0. 1 x 18. 39 = M2 x 9. 1 1. 839/9. 1 = M2 M2 = 0. 202M Trial 2 M1 = 0. 1 (NaOH) V1 = 18. 40mL (NaOH) M2=Unknown (HCl) V2=9. 2mL (HCl) 0. 1 x 18. 40 = M2 x 9. 2 1. 839/9. 2 = M2 M2 = 0. 199M Trial 3 M1 = 0. 1 (NaOH) V1 = 19. 00mL (NaOH) M2=Unknown (HCl) V2=10. 10mL (HCl) 0. 1 x 18. 39=M2 x 9. 1 1. 839/10. 10 = M2 M2 = 0. 182M 2. 0. 202 + 0. 199 + 0. 182/3 = 0. 194 = M average 3. 0. 08233 0. 194 x 100/0. 08233 = 135. 63 percentage error 4.The important concept of this lab was to calculate the unknown molarity of an acid through and through titration. 5. Some of the experiment performed was to determine the concentration of an unknown concentration of an acid through titration by adding a second known concentration acid that will react with and cancel the first one. The endpoint of the titration will allows you to calculate the original concentration. 6. The dilution equation of M1x V1=M2xV2 was required to solve for the molarity of the hydrochloric acid where M1=NaOH(molarity), V1=NaOH(volume), M2=HCl(molarity), V2=HCl(volume). . The lab was successful in the properly changing color to represent a stoichiometric end point through titration. The dilution equation was then used to calculate the unknown molarity of one of the acid. The calculated results werent easily compared due to their decimal placing. References Survey of Chemistry lab manual, Chem 1151 Laboratory Experiments 3rd edition 2011-2012 http//en. wikipedia. org/wiki/Anthocyanin http//en. wikipedia. org/wiki/Titration http//en. wikipedia. org/wiki/Endpoint_%28chemistry%29