12604402
| Question | Answer |
| Name the colour and physical state (at rtp) of F₂ |
Pale yellow
Gas
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| Name the colour and physical state (at rtp) of Cl₂ |
Green
Gas
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| Name the colour and physical state (at rtp) of Br₂ |
Red-brown
Liquid
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| Name the colour and physical state (at rtp) of I₂ |
Grey
Solid
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| Describe and explain the trend in boiling points as you go down Group 7 | The boiling/melting points of the halogens increase down the group. This is due to the increasing strength of the London forces as the number of electrons increases when the size and relative mass of the atoms increases |
| Complete the sentences: A substance is said to be ___________ if it has a low boiling points. So you could say that ___________ decreases down the group | A substance is said to be VOLATILE if it has a low boiling points. So you could say that VOLATILITY decreases down the group |
| In terms of electron transfer, what happens when halogen atoms react? | Halogen atoms react by gaining an electron in their outer shell. This means they're reduced, forming halide ions |
| Give the general formula for the reduction of halogen atoms | X + e⁻ --> X⁻ |
| TRUE OR FALSE: Halogens are oxidising agents | TRUE As halogens get reduced, they oxidise another substance (redox reaction) - so they're oxidising agents. |
| Describe and explain the trend in reactivity down Group 7 | Halogens get less reactive down the group (they become less oxidising) because as you go down the group: Atomic radius increases Shielding increases Nuclear charge increase (effect is overridden) This makes it harder for larger atoms to attract the electron needed to form an ion, so larger atoms are less reactive. |
| Complete the sentences: More reactive halogens will oxidise and _________ the halide ions of less reactive halogens. Reactivity ____________ down the group and so a halogen will displace a halide from solution if the halide is _______ it in the periodic table | More reactive halogens will oxidise and DISPLACE the halide ions of less reactive halogens. Reactivity DECREASES down the group and so a halogen will displace a halide from solution if the halide is BELOW it in the periodic table |
| Which of the halide ions (Br⁻ and/or I⁻) does chlorine displace? | Bromide (Br⁻) and iodide (I⁻) |
| Which of the halide ions (Cl⁻ and/or I⁻) does bromine displace? | Iodide (I⁻) |
| Which of the halide ions (Br⁻ and/or Cl⁻) does iodine displace? | Neither |
| Chlorine displaces bromide (Br⁻). Give the ionic equation for this displacement reaction | Cl₂ + 2Br⁻ --> 2Cl⁻ + Br₂ |
| Chlorine displaces iodide (I⁻). Give the ionic equation for this displacement reaction | Cl₂ + 2I⁻ --> 2Cl⁻ + I₂ |
| Bromine displaces iodide (I⁻). Give the ionic equation for this displacement reaction | Br₂ + 2I⁻ --> 2Br⁻ + I₂ |
| What is the colour of iodine water (I₂)? | Brown |
| What is the colour of bromine water (Br₂)? | Orange |
| What is the colour of chlorine water (Cl₂)? | Colourless |
| When displacement reactions happen, there are colour changes. However, orange and brown can sometimes look similar. What can be done to make the changes easier to see? | Shake the reaction mixture with an organic solvent (e.g. hexane). The halogen that's present will dissolve readily in the organic solvent, which settles out as a distinct layer (solvent layer) above the aqueous solution. Iodine = violet/pink Bromine = orange/red Chlorine = pale yellow/green |
| What is the colour of the solvent layer when iodine is dissolved in an organic solvent (e.g. hexane)? |
Violet/pink
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| What is the colour of the solvent layer when bromine is dissolved in an organic solvent (e.g. hexane)? |
Orange/red
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| What is the colour of the solvent layer when chlorine is dissolved in an organic solvent (e.g. hexane)? |
Pale yellow/green
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| Describe the observations made when chlorine water reacts with potassium bromide solution | Orange/red solution formed with organic solvent |
| Describe the observations made when chlorine water reacts with potassium iodide solution | Violet/pink solution formed with organic solvent |
| Describe the observations made when bromine water reacts with potassium chloride solution | No reaction (solvent layer is orange/red) |
| Describe the observations made when bromine water reacts with potassium iodide solution | Violet/pink solution formed with organic solvent |
| Describe the observations made when iodine water reacts with potassium chloride solution | No reaction (solvent layer is purple/pink) |
| Describe the observations made when iodine water reacts with potassium bromide solution | No reaction (solvent layer is purple/pink) |
| Apart from using displacement reactions, what test could be used to identify halides? | Silver nitrate test |
| Outline the method for the silver nitrate test, including the product formed (and the general ionic equation) if the test is positive | 1. If you are testing solid substances, dissolve each of them separately in distilled water to make solutions 2. Using a pipette, add a few drops of dilute nitric acid (HNO₃) to each test tube 3. Using a pipette, add a few drops of aqueous silver nitrate (AgNO₃) to each test tube If there are chloride, bromide or iodide ions present, a precipitate of the silver halide will be formed: Ag⁺ + X⁻ --> AgX |
| What are the different colours of the precipitate formed when a silver nitrate test is done on chloride, bromide and iodide ions? | CHLORIDE = white BROMIDE = cream IODIDE = yellow |
| It isn't always easy to tell the difference between the precipitates. What can be added to tell the halides apart? | Dilute or concentrated ammonia |
| In the silver nitrate test, why is dilute nitric acid added to the solutions? | The dilute nitric acid gets rid of any unwanted ions that might otherwise mess up the test results |
| Outline the method of adding dilute/concentrated ammonia to the precipitates formed by the silver nitrate test | 1. Using a pipette, add dilute ammonia (NH₃) to each of the silver halide precipitate suspensions 2. If any precipitates haven't dissolved, add concentrated ammonia to the solution |
| Dilute ammonia is added to Cl⁻, Br⁻ and I⁻ solutions. What observations are made? | CHLORIDE = dissolves BROMIDE = insoluble IODIDE = insoluble |
| Concentrated ammonia is added to Br⁻ and I⁻ solutions. What observations are made? | BROMIDE = dissolves IODIDE = insoluble |
| TRUE OR FALSE: The larger the ion is, the more difficult it is to dissolve in ammonia | TRUE |
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