analytical techniques I

Question 1

define volumetric analysis

Answer 1

an analytical technique where the principal measurement is volume - used to analyse solutions

Question 2

define gravimetric analysis

Answer 2

an analytical technique where the principal measurement is mass - use to analyse either solutions or solids

Question 3

define spectroscomy

Answer 3

an analytical technique where the principal measurement is light (electromagnetic radiation) intensity.

involves spectra/absorbance or transmission of specific wavelengths - analyse solutions

Question 4

define chromatography

Answer 4

an analytical or separation technique reliant on the movement of components at different speeds due to their physical properties - analyse or separate mixtures

Question 5

define emission

Answer 5

occurs when excited electrons return to their ground states and radiate energy of fixed wavelengths - emission spectra has coloured lines on black b/ground

Question 6

define absorption

Answer 6

molecules can absorb energy of specific wavelengths - if occurs in visible spectrum then substance = appears coloured. has dark lines on rainbow spectrum

Question 7

define absorbance

Answer 7

the intensity of light remaining after some has been absorbed, compared with the intensity of light when none has been absorbed

Question 8

define transmittance

Answer 8

a measurement of the proportion of light that has been transmitted through a substance, where 100% transmittance means that no energy has been absorbed

Question 9

what is a spectrometer?

Answer 9

an instrument that measures the light emitted or absorbed by excited electrons or molecules

Question 10

define wavelength

Answer 10

the distance between the same point on two successive waves

Question 11

define frequency

Answer 11

the number of waves that pass a given point in one second - HZ

Question 12

electromagnetic spectrum directions

Answer 12

red to violet = increasing frequency
red to violet = increasing energy
red = low energy and violet = high energy
violet to red = increasing wavelength

Question 13

absorption of light - colour wheel

Answer 13

ROY
GVB
complementary colours - if absorbing one colour, observing the complement

Question 14

absorption of light - reflect

Answer 14

something appears to be a particular colour b/c it absorbs the wavelengths of light that are not that colour - so the colour is the only one reflected and not absorbed, so appears as that colour eg red paint

Question 15

absorption of light - transmit

Answer 15

something appears to be a certain colour bc it absorbs the non-colour wavelengths of light, but the actual colour light is not reflected or absorbed, but transmitted = go through eg. cellophane

Question 16

what is a primary standard

Answer 16

a substance whose amount in moles can be calculated accurately from their mass is called a primary standard

Question 17

what are the characteristics of a primary standard

Answer 17

-be readily obtainable in a pure form
-have a known chemical formula
-be easy to store (as solid or solution) without deteriorating or reacting with air
-have a high molar mass to minimise the effect of errors in weighing
-preferable be highly soluble and inexpensive

Question 18

what is the dilution factor

Answer 18

final volume/initial volume

Question 19

substance in conical flask?`

Answer 19

analyte
volume measured out by the pipette is called an aliquot

Question 20

substance in burette?

Answer 20

other substance dispensed slowly into conical flask is titrant, and volume of solution delivered is the titre

Question 21

equivalence point

Answer 21

the point during the titration when the solutions have reacted in exact mole ratios shown by the reaction equation

Question 22

end point

Answer 22

observable point where indicator used in reaction changes colour so signal to stop titration

Question 23

what should the burette and pipette be rinsed with?

Answer 23

with the acid or base being rinsed with

Question 24

what should the volumetric and conical flask be rinsed with?

Answer 24

only with deionised water

Question 25

what is a systematic error

Answer 25

it produces a constant bias in a measurement that cannot be eliminated by repeating the measurement eg. uncalibrated pipette

Question 26

what is a random error

Answer 26

they follow no regular pattern - unpredictable variations

Question 27

components of colorimetry

Answer 27

-a light source that produces light that is absorbed by the solution
-this is passed through a filter to select a particular wavelength
-a glass, plastic or quartz cuvette to hold the sample
-an electronic detector to measure the absorbance of the light that passes through the cell