Redox Titration: Iodometry Experiment

The standard solution employed in most iodometric processes is ______ thiosulfate.

Potassium ______ is an example of a primary standard strong oxidizing agent.

The commercial H2O2 can be titrated by ______ method.

The volume numbers of H2O2 correspond to the amount of available ______.

A 10-volume solution will be about ______ % H2O2 by weight.

Weigh approximately ______ g of Na2S2O3.5H2O and dissolve in distilled water.

Weigh 2 g of ______ into a 100 mL beaker.

Add a few mL of ______ water and swirl for a few minutes until iodine is dissolved.

Weigh 0.25 g of ______ starch and add it to 50 mL of near boiling water.

Dissolve a single tablet in 200 mL of ______ water.

Strain the juice through ______ to remove seeds and pulp.

Cut a 100 g sample into small pieces and grind in a ______ and pestle.

Alcohol may remove _______________ from skin and cleaners are available for fabric stains.

Vitamin C, or _______________, is a water-soluble antioxidant that plays a vital role in protecting the body from infection and disease.

The concentration of the prepared iodine solution can be more accurately determined by titration with a standard solution of _______________ or a standard solution of potassium thiosulfate using a starch indicator.

Ascorbic acid is susceptible to _______________ by atmospheric oxygen over time.

If the samples have to be prepared several hours earlier, oxidation can be minimized by the addition of a small amount of _______________ acid.

Identification of the endpoint in this titration is significantly affected by the _______________ of the sample solution used.

For strongly colored juices there can be a problem with the ______ and it is advised to carry out a “rough” titration in order to become familiar with any distinct color change which occurs at the ______.

This will also help by establishing an approximate volume of ______ solution required.

The above method may be used to carry out a number of interesting investigations regarding the concentration of ______ C in various foods and drinks:

Centre photo: At the ______ all the ascorbic acid has reacted, and the excess ______ reacts with the starch indicator to give a pale blue color.

Figure 2 shows a ______ of commercial fruit juice.

Left photo: before ______, added iodine reacts with ascorbic acid leaving the solution colorless.

The Left flask, before the endpoint, the color of the solution reflects the pale-yellow color of the ______ juice.

In the Centre flask, at the titration endpoint all the ascorbic acid has reacted, and any excess iodine reacts with the ______ indicator to form a dark blue-black complex.

Figure 3 illustrates the titration of ______ juice.

Figure 4 illustrates the titration of ______ capsicum.

The Centre flask, once all the ascorbic acid has been oxidized, a slight excess of added iodine complexes with the ______ indicator, giving the solution a green colour in this case.

The Right flask, if further iodine solution were to be added, the solution's green colour would become darker as shown, due to the formation of further iodine-______ complex.