Vit C conc prac

Question 1

what forms trehalose?

Answer 1

2 alpha glucose molecules

Question 2

what is a monomer

Answer 2

small molecule that reacts with a similar molecule to form a larger molecule, polymers

Question 3

control variables

Answer 3

-storage time
-storage temperature
-type of fruit
-conc of DCPIP

Question 4

what is resolution

Answer 4

the smallest increment of change that can be detected using a measuring instrument (so ruler=1mm)

Question 5

Dependent variable

Answer 5

conc of juice needed to decolourise 1cm3 DCPIP (measured using syringe)

Question 6

independent variable

Answer 6

type of juice

Question 7

method

Answer 7

1. measure set vol of DCPIP into test tube using syringe
2. titrate juice into solution of DCPIP until DCPIP decolourises
   3.record VOL NOT CONC CONC FOUND LATER of juice added in cm3
   4.repeat at least 3 times to calc MEAN conc of juice needed and record results
3. use calibration curve to calc vit c content

Question 8

whats a calibration curve

Answer 8

set of standard samples with known concentrations, used for unkown concs to determine concentration

Question 9

how does calibration curve look on a graph

Answer 9

y-axis=volume cm3 needed to decolourise DCPIP
x-axis=vit c content (mg cm-3)

Question 10

how to use calibration curve graph to find vit c content

Answer 10

use mean results & find volume on y-axis
find intercept & draw line down, value on x-axis is the vit c content