英文版化学实验报告

Acid and alkali neutralization titration curve drawing

The experiment purpose

﹒To master the use of acid, alkali type burette

﹒To study the solution pH is measured by pH meter;

The experimental principle

This experiment adopts the HCl and NaOH solution to titration, which NaOH solution with HCl titration:

NaOH + HCl == NaCl + H2O

At the end of the titration, the solution of pH is 7 (room temperature). At the beginning of the reaction, adding a small amount of alkali or acid just has little effect to the pH caused by neutralization of the concentration of acid or alkali is opposite bigger, at this time based on parallel to X-axis linear titration curve change. When towards the end of the reaction, a small amount of alkali or acid can cause solution pH mutation. Range of different concentration of acid, alkali, mutations is different. The mutation point is the end of the reaction. Using pH meter can continuously monitor the solution’s pH. Record the corresponding pH when the different drip into the volume. With pH of V mapping, this can get the neutralization titration curve, and find a point mutation.

Neutralization titration curve has important significance to quantitatively measure the concentration of alkali or acid experiment in how to choose appropriate ph indicator. Theory of pH indicator discoloration point should be chosen within the scope of the pH mutation, so as to more accurately indicate the finish.

The Experiments use the 0.1 mol/L HCl titrate 0.1 mol/L NaOH and the abrupt range in 4.3 to 9.7. And in sudden change range (4.3 9.7) color indicator according to the principle can be used as indicator.This experiment uses the phenolphthalein as indicator.

Instruments and Reagents

Instruments:PH meter and 100 ml conical flask, acid and alkali burette, hob, 25 ml pipette, washing ears ball

Reagents:distilled water,0.1000 mol/L HCl solution, NaOH solution, Phenolphthalein indicator.

The experimental steps:

Accurately moving 20 ml 0.1000 mol/L HCl solution in the conical flask, and then add 2 ~ 3 drops of phenolphthalein solution in it. Using the PH meter measure the pH titration before the titration. When drop in HCl solution with NaOH solution, you should observe the experiment phenomenon and measure the change of mixed solution PH. when the pH obviously rise, you should slow down the dropping speed. When the pH is near 7, please continue to add standard solution with half drop drops. Every drop measure a pH at a time until the solution change color .And then continue to add to the excessive 1 ~ 2 ml, determination of the pH value. At last please draw the titration curve acid and alkali neutralization.