4. Chemical Analysis Flashcards
What defines a pure element?
A pure element contains only one substance with no other substances mixed in.
How can you assess the purity of a substance?
Purity can be assessed using melting point and boiling point information.
Why are measures of purity important?
Measures of purity are important in everyday substances such as foodstuffs and drugs.
What is a mixture?
A mixture consists of two or more elements or compounds not chemically combined, retaining their individual properties.
How can the substances in a mixture be separated?
Substances in a mixture can be separated by physical methods, including distillation, filtration, and crystallization.
What is paper chromatography used for?
Paper chromatography is used to analyze substances present in a solution, such as food colorings and inks/dyes.
How do you carry out paper chromatography?
Place a spot of the solution on chromatography paper, dip the paper in solvent, and allow the solvent to rise, separating the components.
What is the Rf value in chromatography?
The Rf value is the ratio of the distance moved by the compound to the distance moved by the solvent front.
What are the phases in chromatography?
Chromatography involves a stationary phase and a mobile phase, with separation depending on the relative solubility of the components.
How can chromatography distinguish pure from impure substances?
Pure substances show one spot, while impure substances show multiple spots.
What is the test for hydrogen gas?
A pop is heard when a lighted splint is placed near hydrogen gas.
What is the test for oxygen gas?
A glowing splint relights in a test tube of oxygen gas.
What is the test for carbon dioxide?
Carbon dioxide turns limewater (calcium hydroxide solution) cloudy white.
What are the properties and tests for ammonia gas?
Ammonia has a sharp, choking smell, turns damp red litmus paper blue, and forms white smoke of ammonium chloride with hydrogen chloride gas.
What are the properties and tests for chlorine gas?
Chlorine has a sharp, choking smell, turns damp blue litmus paper red, and then bleaches it white.
What colors do lithium, sodium, potassium, calcium, and barium produce in flame tests?
Lithium: crimson
Sodium: yellow
Potassium: lilac
Calcium: red
Barium: green.
What ions form white precipitates with sodium hydroxide solution, and which one dissolves in excess?
Aluminium, calcium, and magnesium ions form white precipitates; only aluminium hydroxide dissolves in excess sodium hydroxide.
What are the colors of the precipitates formed by copper(II), iron(II), and iron(III) ions with sodium hydroxide?
Copper (II): blue
Iron (II): green
Iron (III): brown.
How do carbonates react with dilute acids, and how can carbon dioxide be identified?
Carbonates react with dilute acids to form carbon dioxide, which turns limewater cloudy white.
What precipitates do halide ions form with silver nitrate solution in the presence of dilute nitric acid?
Silver chloride: white
Silver bromide: cream
Silver iodide: yellow.
What is the test for sulfate ions in solution?
Sulfate ions produce a white precipitate with barium chloride solution in the presence of dilute hydrochloric acid
