Chemical Analysis Flashcards
What is a pure substance in chemistry?
A substance made of only one type of element or compound, with a fixed boiling and melting point.
How can you tell if a substance is pure?
It has a sharp melting and boiling point (impurities lower the melting point and raise the boiling point).
What is a mixture?
A combination of two or more substances not chemically bonded, with a range of boiling and melting points.
Give an example of a pure substance and a mixture.
Pure substance: Distilled water (H₂O).
Mixture: Seawater (contains salts, minerals, and water).
What is chromatography used for?
To separate and identify substances in a mixture, such as dyes in ink or food colorings.
What are the two phases in chromatography?
Mobile phase (solvent that moves) and stationary phase (paper or chromatography plate).
Why do different substances move different distances in chromatography?
Because they have different solubilities and attractions to the stationary phase.
How can chromatography be used to identify unknown substances?
By comparing Rf values to known substances in a database.
What would it mean if a chromatogram shows only one spot?
The substance is pure.
What is the test for hydrogen gas?
A lit splint in hydrogen gas produces a squeaky pop sound.
What is the test for oxygen gas?
A glowing splint in oxygen relights.
What is the test for carbon dioxide gas?
Bubble the gas through limewater; it turns cloudy/milky.
What is the test for chlorine gas?
Damp blue litmus paper turns red, then bleaches white.
