Gorup 7 Flashcards
Chlorine has a low boiling point because the forces between the molecules are weak.
Explain how these forces arise between molecules of chlorine.
(a)
(Random) movement of electrons in one molecule (creates a dipole) / a (temporary) dipole is formed in one molecule / an imbalance in
Induces a dipole in a neighbouring molecule.
(These) temporary dipoles attract / temporary attraction between delta+ and delta-
D
A
(b) A solution that is thought to contain chloride ions and iodide ions is tested.
Dilute nitric acid is added to the solution.
Aqueous silver nitrate is added to the solution.
A pale yellow precipitate forms.
Excess dilute aqueous ammonia is added to the mixture.
Some of the precipitate dissolves and a darker yellow precipitate remains.
Give a reason for the use of each reagent.
Explain the observations.
Give ionic equations for any reactions.
A student was given a 50.0 g sample of solid silver chloride contaminated with solid silver carbonate.
The student suggested the following method to obtain the maximum amount of pure dry silver chloride from the sample:
1. Tip the solid into a boiling tube.
2. Add dilute nitric acid.
3. Allow the remaining solid to settle.
4. Decant off the liquid.
5. Leave the sample to dry on a shelf.
Identify any faults or omissions in the method suggested by the student.
Suggest improvements to the method, using commonly available laboratory equipment.
The following chemicals are also available:
distilled water, dilute solutions of NaOH, NH3, HCI, H2SO4
This question is about elements in Group 7 of the Periodic Table and their
(a) Bromine (Br2), strontium chloride (SCI2) and iodine monochloride (ICI) all have similar M values.
Suggest, with reasons, the order of melting points for these three substances.
Suggest a disadvantage to adding chlorine to drinking water
Wasteful as most potable water not used for drinking
Some people suffer eye irritation
Some people find taste unpleasant
Bromine reacts with phosphorus to form phosphorus tribromide.
Write an equation for this reaction and draw the shape of the phosphorus tribromide molecule formed.
Suggest the bond angle in phosphorus tribromide.
Sodium bromide reacts with concentrated sulfuric acid in a different way from sodium chloride.
Write an equation for this reaction of sodium bromide and explain why bromide ions react differently from chloride ions.
A colourless solution contains a mixture of sodium chloride and sodium
Using aqueous silver nitrate and any other reagents of your choice, develop a procedure to prepare a pure sample of silver bromide from this mixture.
Explain each step in the procedure and illustrate your explanations with equations, where appropriate.
A
D
Suggest one reason why the reaction of sodium fluoride with concentrated
sulfuric acid is different from the reaction with sodium iodide
Fluoride less powerful reducing agent (than iodide)
Fluoride less easily oxidised than iodide
(b) The pool manager maintains the water at a pH slightly greater than 7.0
Explain how this affects the equilibrium established when chlorine is added to water.
Hydroxide / alkali ions react with the acids
Equilibrium moves to the right
Explain why the solution of strontium chloride was filtered to remove insoluble impurities before the addition of silver nitrate.
Would give an incorrect / too large mass (of silver chloride)
Calcium ethanoate, (CH3COO)Ca2 is used in the treatment of kidney disease
Thermal decomposition of calcium ethanoate under certain conditions gives propanone and one other product.
Write an equation for the thermal decomposition of calcium ethanoate.
State the trend in the oxidising abilities of the elements down Group VIl from chlorine to iodine
Explain how this trend can be shown by displacement reactions between halogens and halide ions in aqueous solutions.
Illustrate your answer with appropriate observations and equations.
Deduce a half-equation for the oxidation of SO2 in aqueous solution forming
SO42- and H+ ions.
D
Deduce the identity of a carbon-containing species formed when methanoic acid reacts with Tollens’ reagent.
Draw the structure of methanoic acid. By reference to this structure, suggest why a silver mirror is formed when this acid reacts with tollens
Draw the structure of ethanoyl chloride. Predict what, if anything, you would observe when ethanoyl chloride is added to aqueous silver nitrale.
(c)How can reactions with concentrated sulphuric acid be used to distinguish between solid
samples of sodium bromide and sodium iodide?
State the observations you would make and give all the oxidation and reduction products formed in both reactions. Using half-equations, construct an overall equation for one of these redox reactions.
(b)
Write an equation for Extraction Process 2 and an equation for Extraction Process 3.
Calculate the percentage atom economy for the extraction of bromine from potassium bromide by Extraction Process 3. Suggest why Extraction Process 3 is the method in large-scale use today.
