Chemical Analysis Year 11 Flashcards
define purity and give an example of a pure substance
a single element/compound that is NOT mixed with any other substance
ie diamond
give the formula for RF value
distance COMPONENT traveled/distance SOLVENT traveled
what should RF value be given to (sf)
2sf
what numbers should RF value be between
0 and 1
what does the distribution of the components in the sample depend on
relative attraction to the paper and solvent
define a formulation
PURE substances carefully mixed in specific proportions to have desired propertied
what can RF values be used for
to identify substances in a solvent
comment on RF values from substance to substance
different compounds have different RF values
what is the gas test for hydrogen
lighted splint emits a squeaky pop
what is the gas test for oxygen
glowing spilt will relight
what is the gas test for CO2
turns limewater from clear to cloudy
what is the gas test for chlorine
turns BLUE litmus paper RED the bleaches it
describe the importance of gas tests
must identify substances present for:
- safety
- helps to identify substances present
what is the trend of melting/ boiling points for pure substances
the all have very specific temperatures
give substances where purity is especially importants
- medication
- baby food
- cosmetics
give a possible suggestion of a melting point of a pure substance
88-89*C
give examples of formulations
- alloys
- fertilisers
- gold jewellery
state the speed at which substances with a stronger attraction to the paper will travel
slower and move less far up the paper
state the speed at which substances with a weaker attraction to the paper will travel
faster and move further up the paper
what is RF value
ratio of distance moved by substances to solvents
how could RF values be different if different solvents/stationary phases are used
the substances could have a stronger/ weaker attraction to the stationary phase so they would move quicker/slower therefore RF value is altered
how could RF values be different if different solvents are used
solvents could be less soluble so wouldn’t dissolve all of the compounds
what are the two phases called in chromotography
-
in paper chromatography, how many spots will a pure substance form on the paper
-
give the formula for working out the Rf value of a substance
-
how can you test if a gas in a test tube is oxygen?
-
describe how paper chromotography works to separate mixtures
-
what colour does litmus paper turn in the presence of chlorine
- white (if it goes red for a moment its bc chlorine is acidic)
would you expect the Rf value of a substance to change if you changed the solvent in the chromatography experiment. why?
-
a student collects gas given off during a reaction & bubbles go through limewater. the limewater goes cloudy. identify the gas produced
- carbon dioxide
