Preparation of standard solutions of acids and bases and comparative experiments
Preparation of standard solutions of acids and bases and comparative experiments
This experimental method was obtained from the official website of the Fourth Military Medical University
Operation method
Preparation of standard solutions of acids and bases and comparative experiments
Principle
NaOH easily absorb water vapor and CO2 in the air. hydrochloric acid is easy to volatilize and release HCl gas, so they can not use the direct method of preparation of standard solutions, can only use the indirect method of preparation, and then calibrated with the reference material to determine its exact concentration. When the acid-base reaction reaches the theoretical end point, CNaOHVNaOH = CHClVHCl usually in the case of error, according to the volume of acid-base solution ratio, as long as to determine the concentration of any one of these solutions, you can calculate the exact concentration of another solution.
Materials and Instruments
NaOH solid Concentrated HCl 0.1mol/L HCl 0.1mol/L NaOH Methyl orange Phenolphthalein Move 1. Preparation of HCl solution Measure 3.5mL of concentrated HCl with a clean measuring cylinder, dilute it to 500mL with distilled water, transfer it to a milled reagent bottle, cover the stopper, shake it well, and label it for spare use. Caveat 1. note the rate of titration at the endpoint;2. learn the half-drop operation;3. Judge the end point, pay attention to master 0.5min does not fade;4. Environmental protection tips: HCI is volatile and irritating, pay attention to ventilation, acid and alkali solutions should be neutralized before discharge. For more product details, please visit Aladdin Scientific website.
500mL glass stoppered spouted flask 10mL measuring cylinder 500mL rubber stoppered spouted flask 250mL beaker Bench scale 50mL acid burette 50mL alkaline burette 250mL conical flask
2. Preparation of NaOH solution with a beaker by the balance quickly weigh 2g of solid NaOH, add about 30mL of distilled water without CO2 to dissolve, dilute to 500mL, transferred to a rubber stoppered reagent bottle, covered with a good stopper, shaken well, labeled and spare. Label with: reagent name, concentration, date of preparation, specialty, and name.
3. Titration exercise
(1) Put 10mL of 0.1mol/L NaOH solution into a conical flask, add 10mL of distilled water, add 1-2 drops of methyl orange indicator, and titrate with 0.1mol/L HCl solution until it changes from yellow to orange.
(2) From the "acid tube" release 10mL 0.1mol ／ L HCl solution in another conical flask, add l0mL distilled water, then add 1 drop of phenolphthalein indicator, with 0.1mol ／ L NaOH solution titration to the end point (reddish), 0.5min does not fade.
(3) Acid and alkali drop back to each other, repeatedly identify the end point color, control the titration speed.
4. Comparative titration of acid-base standard solutions
(1) acid (alkali) burette were loaded with "standard solution" to zero above the scale, and adjust the liquid level to "0.00" near the scale, and accurately record the initial reading.
(2) From the alkali tube at a flow rate of 10mol ／ L min release 20ml (read to 0.01 mL) of NaOH solution to the conical flask, add 1 to 2 drops of methyl orange, titrate with HCI standard solution until the solution turns from yellow to orange, record the volume of HCI solution consumed.
(3) Determine 2 to 3 times in parallel. (The acid and base solutions must be refilled near the zero mark of the buret for each determination.