Chemical Analysis Flashcards
(28 cards)
When is equilibrium achieved?
When rate of the forward reaction is equal to the rate of the backward direction
What are pure substances in terms of melting point?
Melt + solidify at one temp
What are pure substances in terms of boiling point?
Boil + condense at one temp
Describe pure substances?
•Melt + solidify at one temp
•Boil + condense at one temp
What do pure substances consist of?
Only one type of element or one type of compound
What is a closed system?
Where no reactants are added and no products are removed
What will a pure substance produce during chromatography?
A single spot in all solvents
What will a mixture in chromatography produce?
Different spots depending on solvent
Test for carbon dioxide?
•Limewater (colourless)
•CO2 bubbled through it
•Limewater goes cloudy/milky
Test for hydrogen?
Put a lit splint into a test tube with hydrogen gas, makes squeaky pop
Test for oxygen?
Put a glowing (no flame) splint inside glass jar, will relight if oxygen present
Why do we draw the starting point line in pencil during chromatography?
If it was pen, pen ink would move up paper with solvent
Test for chlorine gas?
-Use sodium chloride+electrolysis
-Turn power pack on
-Starts bubbling
-Hover damp litmus blue paper over bubbling gas
-Chlorine present if paper turns white/bleach it
Hoe do you find Rf value? (Chromatography)
Distance moved by substance ÷ distance moved by solvent
What is the Rf value used to identify (chromatography)?
Identify components in an unknown substance in chromatography
What is a problem with using the Rf value?
Many substances have same Rf or some may never have been analysed on database
How do you fix the problem if the substance you used had the same Rf as another?
Repeat with different solvent
What is the stationary phase in chromatography?
Doesn’t move (absorbent paper)
What is the mobile phase in chromatography?
Does move (solvent, often 💧)
What is chromatography?
Separates mixtures into their individual components
What does water do in chromatography?
Dissolves samles, carries them up paper
In chromatography why do components move different distances?
Depends on attraction for the paper and solvent
Examples of using chromatography?
To know what pen colours contain more than one colour
