basic operations in analytical chemistry

Question 1

what does analytical balance measure

Answer 1

it is used to measure masses with high accuracy

Question 2

what are the 3 types of analytical balance (and its capacity)

Answer 2

macrobalances (160-200g)
semimicroanalytical (10-30g)
microanalytical (1-3g)

Question 3

true or false
center the load on the pan in the analytical balance

Answer 3

true

Question 4

true or false
adjust the analytical balance yourself if it needs adjustment

Answer 4

false - ask an instructor

Question 5

true or false
keep the balance scrupulously clean only

Answer 5

false - and it’s case too

Question 6

true or false
always allow an object to cool down to room temperature before weighing it in the analytical balance

Answer 6

true

Question 7

why do we use tongs, finger pads or a glassine paper strip to handle dried objects

Answer 7

to prevent transferring moisture to them

Question 8

what equipment do you use for removing spilled material or dust in the analytical balance

Answer 8

camel’s hair brush

Question 9

low precision balance should be used when …

Answer 9

high sensitivity is not required

Question 10

it is well- used for larger, messier samples that are raw or need to be processed.

Answer 10

top-loading balance

Question 11

what is being cooled in a desiccator before weighing

Answer 11

oven-dried sample or reagents

Question 12

true or false
failure to allow sufficient time for a heated object to return to room temperature is the most common source of the problem

Answer 12

true

Question 12

attempts to weigh an object whose temperature is different from that of its surrounding will result in…

Answer 12

significant error

Question 13

desiccator

Answer 13

keep samples dry while they are cooling and before they are weighed in

Question 14

muffle furnace

Answer 14

ignite sample to high temperatures
(either to convert precipitates to a weighable form or
burn organic materials prior to inorganic analysis)

Question 15

oven

Answer 15

dry samples prior to weighing

Question 16

hood

Answer 16

trap and exhaust vapors, gases and nanoparticles

Question 17

when do we use fume hood

Answer 17

when chemicals or solutions are to be evaporated

Question 18

wash bottles

Answer 18

wash precipitates

Question 19

it is used for quantitative transfer of precipitates and solutions

Answer 19

wash bottle

Question 20

centrifuge

Answer 20

it is where blood may have to be separated into fractions such as serum or plasma and proteins may have to be separated by precipitation followed by centrifuging

Question 21

it has many useful applications, particularly in clinical laboratory

Answer 21

centrifuge

Question 22

it permit the transfer of accurately known volumes from one container to another.

Answer 22

pipets

Question 23

what are the types of pipets

Answer 23

1. volumetric/ transfer
2. measuring/ graduated
   - mohr
   - serological

Question 24

true or false:
the final volume of solution must be blown out from the tip to deliver the calibrated amount.

Answer 24

true

Question 25

identify the available capacity based on the pipets
volumetric-
mohr-
serological-

Answer 25

volumetric- 1-200 mL
mohr- 1-25 mL
serological- 0.1-10 mL

Question 26

this pipet delivers a single and fixed volume. used for accurate measurement since it is designed to deliver only one volume and s calibrated at that volume

Answer 26

volumetric pipet

Question 27

this pipet are straight- bore pipets that are marked at different volume intervals.

Answer 27

measuring pipets

Question 28

difference between serological and mohr pipet

Answer 28

seriological - blown out
mohr - not blown out like volumetric

Question 29

true or false:
when transferring liquid using the volumetric pipet, it is important to use your thumb to stop the flow of liquid

Answer 29

false- use your index finger instead because thumb tends to have larger areas of contact = less control of releasing pressure

Question 30

it is a common yet essential laboratory instrument used to accurately and precisely transfer volumes of liquid in the microliter range

Answer 30

micropipettes

Question 31

this pipet is available in single-
channel and multi- channel variants. it is also available in different designs and sizes

Answer 31

micropipettes

Question 32

which instrument is commonly used in titrations

Answer 32

burets

Question 33

they are used for the preparation of
standard solutions and for the dilution of samples to a fixed volume prior to taking aliquots with a pipet.

Answer 33

volumetric flask

Question 34

Aliquot

Answer 34

fraction of solution

Question 35

this equipment is considered more accurate and precise for measurement purposes than flasks and beakers but should not be used for volumetric analysis

Answer 35

graduated cylinder

Question 36

a marked curvature at the top surface of a liquid confined in a narrow tube

Answer 36

meniscus

Question 37

meniscus:
* Clear liquid –
* Colored and opaque liquid –

Answer 37

• Clear liquid – lower meniscus
• Colored and opaque liquid – upper
  meniscus

Question 38

is a condition that causes the
volume to appear smaller than its actual value if the meniscus is viewed from above and larger if the meniscus is viewed from below.

Answer 38

parallax