4.8 Chemical analysis Flashcards
(24 cards)
What is a pure substance?
A substance containing only one element or compound with a fixed boiling/melting point.
What is a formulation?
A useful mixture with exact amounts of components, designed for a specific purpose.
What is chromatography used for?
To separate and identify substances in a mixture.
What does the Rf value mean?
Rf = distance travelled by substance ÷ distance travelled by solvent.
How do you test for hydrogen?
Use a lit splint; a ‘squeaky pop’ confirms hydrogen.
How do you test for oxygen?
A glowing splint relights in the presence of oxygen.
How do you test for carbon dioxide?
Bubble through limewater; it turns cloudy if CO₂ is present.
How do you test for chlorine?
Damp blue litmus paper turns red then bleaches white.
What flame colour does lithium produce?
Crimson red.
What flame colour does sodium produce?
Yellow.
What flame colour does potassium produce?
Lilac.
What flame colour does calcium produce?
Orange-red.
What flame colour does copper produce?
Green.
What precipitate forms with Al³⁺ and NaOH?
White precipitate, dissolves in excess NaOH.
What precipitate forms with Ca²⁺ and NaOH?
White precipitate, does not dissolve in excess.
What precipitate forms with Mg²⁺ and NaOH?
White precipitate, does not dissolve in excess.
What precipitate forms with Cu²⁺ and NaOH?
Blue precipitate.
What precipitate forms with Fe²⁺ and NaOH?
Green precipitate.
What precipitate forms with Fe³⁺ and NaOH?
Brown precipitate.
How do you test for carbonates?
Add dilute acid; CO₂ gas will turn limewater cloudy.
How do you test for sulfates?
Add HCl and barium chloride; a white precipitate confirms sulfate.
How do you test for halides?
Add nitric acid and silver nitrate: chloride=white, bromide=cream, iodide=yellow.
What is flame emission spectroscopy?
An instrument-based method to identify metal ions and concentrations from their emission spectra.
