Question

ОООО At a pH of 9.5, would you expect p-nitrophenol to be: ionized and yellow in color un-lonized and yellow in color Ionized and colorless un-lonized and colorless 1 points Save A and QUESTION 4 The Beer-Lambert Law states that the fraction of light absorbed is proportional to the spectrophotometer used and the temperature of the solution the time the sample is measured for and the path length the path length and the concentration of the solution in which the light passes through the concentration of the solution and the spectrophotometer used 1 points Save Answer QUESTIONS In lab this week, students will be using a spectrophotometer to measure the absortance of various solutions, which statement below is correct The samples must be placed in the 1ml cuvette from your locker prior to measuring the absorbance using the spectrophotometer A test tube can be directly inserted into the spectrophotometer The placement of the cuvette into the spectrophotometer is not important The samples must be placed in the 3ml cuvette from your locker and the cuvette must be placed into the spectrophotometer in a specific orientation to measure the absorbance

Answer 1

Question 3:

Answer is first option-ionised and yellow colour.

Explanation:

Para nitrophenol is used as a pH indicator ,because para nitrophenol is colourless at pH below 4.5 and yellow above 7.5.Yellow colour is due to ionisation of paranitrophenol(deprotonated)to form 4-nitrophenolate.

Question 4:

Answer is third option-the path length and concentration of the solution which the light passes through.

Beer-Lambert law states that fraction of light absorbed is proportional to the path length and concentration of solution which the light passes through.

A=£Cl . ;Where

A-absorbance

£-constant

C-concentration of solution

l-path length

Question 5:

Answer is fourth option-The sample must be placed in3 ml cuvette from your locker andthe cuvette must be placed in the spectrophotometer in a specific orientation to measure the absorbance.

Explanation:

Cuvettes have 2 clear sides and 2frosted sides.There will be an arrow at the top of one clear side.This shows which side of cuvette should be oriented towards spectrophotometer beam.It is important because rotation of cuvette by 180 degree will give different readings.