Some Lab stuff and Titratable Acidity

Question 1

Design an experiment to assess accuracy and precision of an assay

Answer 1

Measurement experiment from class. Triplicates at least of data created and have a target amount of water to deliver. Finding the SD and CV as well as Error values will indicate accuracy and precision

Question 2

Standard Deviation equation

Answer 2

know it

Question 3

Coefficient of variation equation

Answer 3

CV= (SD/Mean) *100

Question 4

what fractoin of a normally distributed data set can be found within 1, 2 and 3 SD of the mean

Answer 4

3SD = 100%
2SD= 95%
1SD = 68%

Question 5

Is higher or lower SD more precise?

Answer 5

Lower SD, the points are closer together

Question 6

Confidence interval equation

Answer 6

Mean +/- Z value * SD/SQRT(n)

z value for 95% confidence is 1.96

Question 7

Systematic Error

Answer 7

Results consistently deviate from true value (ex. pipettor calibrated incorrectly)

Question 8

Random Error

Answer 8

Can fluctuate and are avoidable (Ex. differences between balances)

Question 9

Blunders

Answer 9

Big screw-ups (Ex. pipetting .5 mL instead of 1 mL)

Question 10

Sensitivity

Answer 10

Change in the response of a system for a small change of the stimulus causing the response

Question 11

Limit of detection

Answer 11

Lowest quantity of a substance that can be distinguished from the absence of that substance within a standard confidence limit

Question 12

Units for Normality

Answer 12

Equivalent/L

Question 13

how many N in lactic acid and sulfuric acid from a 0.5M soluition

Answer 13

0. 5 N lactic acid

1. 0 N sulfuric acid

Question 14

Equivalent weight

Answer 14

Molecular weight/number of equivalence Ex. EqWt H2SO4 = 98/2 = 49

Question 15

Titratable Acidity Equation

Answer 15

%Acid = (NV1EqWt)/(V2*10)

N-normality titrant V1-volume titrant EqWt-equivalent wt of predominant acid V2-volume sample

Question 16

Titratable acidity

Answer 16

a measure of the concentration of intrinsic acid in foods

Question 17

Apparent acidity

Answer 17

Natural acidity which is due to citrates and phosphates etc.

Question 18

Fixed acidity

Answer 18

Non-volatile acids

Question 19

Volatile acidity

Answer 19

the steam distillable acids present in wine primarily acetic acid

Question 20

Predominant acid

Answer 20

Titratable acidity is expressed in terms of this. Main acidic element int the food

Question 21

Set up an experiment to determine TA

Answer 21

Known weight of a food sample is titrated using a standard base to a phenolphthalein endpoint. the volume of the titrant is used along with the Normality of the base and the wt. of the sample to calculate TA

Question 22

Phenolphthalein indicator function and advantages

Answer 22

changes color from clear to red in the range of pH 8-9.6

Food acids do not buffer at this pH (8.2)