Thermal stability and flame coloursEdexcel International A Level Chemistry: Flashcards
What these 14 flashcards ask
- Which flame colour does lithium give?
- Which flame colour does sodium give?
- Which flame colour does potassium give?
- Which flame colours do calcium and barium give?
- Explain how a flame colour arises.
- Write the general equation for decomposition of a Group 2 carbonate.
- Write the equation for sodium nitrate on heating.
- Write the equation for magnesium nitrate on heating.
- State the trend in thermal stability of Group 2 carbonates and nitrates.
- Why does thermal stability increase down Group 2?
- Which Group 1 compounds behave like Group 2 compounds when heated?
- Give the test for carbon dioxide.
- Give the test for oxygen.
- How do you recognise nitrogen dioxide?
Exam questions on Thermal stability and flame colours
- A technician identifies the metal in unlabelled solid samples by flame tests. She dips a clean nichrome wire into each sample, holds it in the edge of a blue Bunsen flame and records the colour. The samples contain compounds of lithium, potassium, calcium and barium.Explain, in terms of electrons, how the heated metal ions produce coloured light.2 marks
- Samples of magnesium carbonate and barium carbonate are heated strongly in turn in a hard-glass test tube under identical conditions, and any gas given off is passed through limewater. Magnesium carbonate decomposes at a much lower temperature than barium carbonate.Explain why barium carbonate decomposes at a higher temperature than magnesium carbonate.2 marks
- A student heats small samples of sodium nitrate and calcium nitrate in separate dry test tubes. Both tubes give off a colourless gas that relights a glowing splint, but only one of them also gives off a brown gas.Write equations for the thermal decomposition of sodium nitrate and of calcium nitrate. State which tube gives the brown gas, naming it and giving its effect on damp blue litmus paper.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).