Chemical Tests
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What is the test for hydrogen gas?
• Hold a lighted splint above the mouth of a test tube • If hydrogen is present, it will burn with a squeaky pop
What is the test for oxygen gas?
• Hold a glowing splint inside of a test tube • If the splint relights, oxygen is present
What is the test for chlorine gas?
• Use litmus paper • If it is bleached, than chlorine gas is present Chlorine gas is also visible, with a yellow-green colour
What is the test for ammonia gas?
• Use damp red litmus paper • If ammonia is present, it will turn blue
What is the test for carbon dioxide gas?
• Bubble it through lime-water (calcium hydroxide) • If it turns milky/cloudy, it is carbon dioxide as calcium carbonate will have formed
Why must a metal like nichrome or platinum be used when doing a cation flame test?
• It is unreactive and will not burn with a colour • It has a high enough melting point to not melt under a flame
Why must you clean the platinum or nichrome wire in concentrated acid before doing a cation flame test?
To avoid contamination so only one ion is present when doing the flame test
What is the colour of the flame when lithium ions are burning?
Red
What is the colour of the flame when sodium ions are burning?
Yellow
What is the colour of the flame when potassium ions are burning?
Lilac
What is the colour of the flame when calcium ions are burning?
Orange-Red
What is the colour of the flame when copper ions are burning?
Blue-green
What is the test for copper ions in an aqueous solution?
• Add sodium hydroxide solution • If copper ions are present, there will be a blue precipitate
What is the test for iron (II) ions in an aqueous solution?
• Add sodium hydroxide solution • If iron (II) ions are present, there will be a green precipitate
What is the test for iron (III) ions in an aqueous solution?
• Add sodium hydroxide solution • If iron (III) ions are present, there will be a red-brown precipitate
What is the test for ammonium?
• Add sodium hydroxide solution • If ammonium ions are present, ammonia gas will be released which can be tested for by observing damp red litmus paper turning blue
What is the test for carbonate ions?
• Add a dilute acid (like hydrochloric acid) to the solution • If it bubbles, and those bubbles turn calcium hydroxide solution (limewater) cloudy/milky then carbonate ions are present (because carbon dioxide gas is released)
What is the test for sulfate ions?
• Add dilute hydrochloric acid • Then add barium chloride • If there is a white precipitate, sulfate ions are present
What is the test for chloride ions?
• Add dilute hydrochloric acid • Then add silver nitrate • If there is a white precipitate, chloride ions are present
What is the test for bromide ions?
• Add dilute hydrochloric acid • Then add silver nitrate • If there is a cream precipitate, chloride ions are present
What is the test for iodide ions?
• Add dilute hydrochloric acid • Then add silver nitrate • If there is a yellow precipitate, chloride ions are present Summary note: For tests in inorganic chemistry, you to indentify the ions within an ionic compound so you need to do a cation test and an anion test
How do you test for water?
• Add to anhydrous (dry) copper(II) sulfate solution • It will turn from white to blue if it is water which is added
How do you test for the purity of a sample of water?
• Boil the sample at 100 degrees celcius to check if the boiling point is exactly 100 • Any impurities will raise the boiling point and depress the melting point