(r) quantitave methods to determine the concentration of a chemical substance iin a solution

How do you make a dilution series?

Using distilled water

1.00% is just as it is

0.50% take half (5cm³) the 1.00% and then add half water.

Then add 5cm³ of that 0.50% and do 0.25%

Why are equal volumes used?

Ensure a fair comparison

What happens with the benefits reagent?

Reacts with reducing blue cu²+ ions to brick red cu2O precipitate

Why do we centrifuge?

Separates the precipitation from the remaining solution.

Allows colorimeter to measure only the supernatant ( liquid on top)

The more glucose the more ———-

The more glucose the moe cu²+ gets reduced so less blue dye remains.

Higher glucose = higher transmission of red light

Why does transmission of red light increase as glucose concentration increases?

More glucose - more reduction of cu²+ - less blue copper ions left - less blue colour in solution

Less blue = higher transmission of re light through the sample

Why is it necessary to centrifuge before colorimeter readings?

To remove the precipitate which would scatter light and give inaccurate results.

Colorimeter only accurately measures the clarity (absorbance/transmisssion) of a solution