chem lab (analysis2)

Question 1

what are the other spectroscopic method basing on
the wavelength range

Answer 1

*IR spectrophotometer
*UV-VIS spectrophotometer

Question 2

IR spectrophotometer?

Answer 2

*uses light over the infrared range (700 – 15000 nm) of electromagnetic radiation spectrum.

Question 3

UV-VIS
spectrophotometer

Answer 3

• uses light over the ultraviolet range (185 – 400 nm) and visible range (400 – 700 nm) of electromagnetic radiation spectrum.
  *Absorption or transmission of a certain substance can be determined by the observed color.
• If a solution sample absorbs red light (~700 nm), the solution will appear (transmit) green because it is the complementary color of red

Question 4

Basic
spectrophotometers are
consist of the following:

Answer 4

◦ Light source
◦ A collimator
◦ A monochromator
◦ Wavelength selector
◦ Cuvette for sample
solution
◦ Photoelectric detector
◦ Digital display or a
meter

Question 5

Important concepts relating
to spectrophotometers

Answer 5

The amount of light from the light source that passes through the cuvette and into the detector is dependent on the length of the cuvette and the concentration of the sample.

Question 6

Once the intensity of light that passes through the sample in the
cuvette is known, this can be related to its transmittance. what is the formula for this?

Answer 6

transmittance (T)= It/Io

Question 7

what is It?

Answer 7

the light intensity after the beam of light passes through the
cuvette

Question 8

what is Io

Answer 8

the light intensity before the beam of light passes through the cuvette.

Question 9

absorbance

Answer 9

stands for the amount of light that is absorbed.

Question 10

Once the absorbance is known using this equation, the
concentration of an unknown solution can be determined
using the Beer-Lambert Law. true or false?

Answer 10

true

Question 11

what is a calibration curve?

Answer 11

regression model used to predict the unknown concentrations of analytes of interest based on the response of the instrument to the known standards.

Question 12

calibration curve is made by preparing?

Answer 12

made by preparing a set of standard solutions at various concentrations with a range that includes the unknown of interest. These solutions are then read in the instruments to obtain their corresponding instrument response.

Question 13

a plot is made by?

Answer 13

made from the concentrations of each standard solution
and its corresponding instrument response.

Question 14

what analyses are essential parameter of water quality?

Answer 14

phosphates, nitrates in water

Question 15

pH meter

Answer 15

Measures the acidity or alkalinity of the solution

Question 16

The working principle behind pH meters is?

Answer 16

potentiometry

Question 17

what is potentiometry?

Answer 17

the measurement of a solution’s electric potential (voltage).

Question 18

electric potential is?

Answer 18

ability to conduct a current

Question 19

these 2 can efficiently conduct an electric current because of the positive hydrogen ions.

Answer 19

H+ or H3O+

Question 20

Principle behind pH meters

Answer 20

The pH meter measure electric potential using two electrodes
inserted into the liquid to create an electrical circuit.

Question 21

One electrode is called?

Answer 21

the reference electrode (contains a substance with known electric potential)

Question 22

The second electrode, known as

Answer 22

the sensor electrode, is the one that will be inserted into the solution being tested.

Question 23

pH meters should be calibrated with the appropriate buffer
solutions at?

Answer 23

pH 7, pH 4 and pH 10