Group 7 Chapter 10 Flashcards
At room temperature what is fluorine like?
A pale yellow gas.
At room temperature what is chlorine like?
A pale green gas.
At room temperature what is bromine like?
A red-brown liquid.
At room temperature what is iodine like?
A black solid?
What is the trend in appearances going down group 7, why?
Darker and denser, larger m.p and b.p down the group and less volatile down the group.
What is the trend in size of atoms down group 7, why?
Bigger down the group, extra electron shell filled.
What is the trend in electronegativity going down group 7, why?
Decreases, bigger the atoms the more the nucleus is shielded by extra inner e-s meaning effect of nuclear charge is reduced and so is the nucleus’ ability to attract the pair of e-s.
What is the trend of melting and boiling points down group 7, why?
Increase, larger atoms have more e-s making VDW forces between molecules stronger.
How do halogens usually react, what does this make them . What sort of reaction is this and why?
React by stealing e-s to become negative ions. This is a redox reaction as halogens are oxidising agents and are themselves reduced.
What is the trend in oxidising ability of halogens going down the group?
Decreases down the group, increases up the group.
What halogen is one of the best oxidising agents known?
Fluorine.
How do halogens react with metal halides in solution?
The halide in the compound will be displaced by the more reactive halogen, displacement reaction.
Does F2 oxidise Cl-?
Yes.
Does F2 oxidise Br-?
Yes.
Does F2 oxidise I-?
Yes.
Does Cl2 oxidise F-?
No.
Does Cl2 oxidise Br-, what does it produce and what is the equation?
Yes, yellow/ orange solution. Cl2(aq) + 2Br-(aq) -> 2Cl2-(aq) + Br2(aq).
Does Cl2 oxidise I-, what does it produce and what is the equation?
Yes, brown solution and black precipitate. Cl2(aq) + 2I- -> 2Cl-(aq) + I2(aq).
Does Br2 oxidise F-?
No.
Does Br2 oxidise Cl-?
No.
Does Br2 oxidise I-, what does it produce and what is the equation?
Yes, brown solution and black precipitate. Br2(aq) + 2I-(aq) -> 2Br-(aq) + I2(aq)
Does I2 oxidise F-?
No.
Does I2 oxidise Cl-?
No.
Does I2 oxidise Br-?
No.
Which halogen is the weakest oxidiser?
Iodine.
Which halogen is the strongest oxidiser?
Fluorine.
When displacing a species, when the weaker one is left alone what is its state?
Solid.
When a halide ion reduces another substance, what happens and what is the general equation?
Halide is oxidised to a halogen, 2X- -> X2 + 2e-`
What is the trend in reducing power down group 7 halides, why?
Increases, larger the ion the easier it is to lose e-s.
How do we test the reducing power of the halides?
Solid Na halides react with concentrated sulphuric acid. he products are different and reflect their reducing power.
Drops of sulfuric acid are added to sodium CHLORIDE, what is the product? What type of reaction is this and what is the equation?
Produces steamy fumes of HCl, the solid product is sodium hydrogen sulphate. This is an acid-base reaction and the equation is NaCl + H2SO4 -> NaHSO4 + HCl.
Is the reaction with sodium chloride a redox, why or why not?
No, no oxidation state has changed.
Drops of sulfuric acid are added to sodium BROMIDE, what are the products? What type of reactions are these and what are the equations?
Steamy fumes of HBr, brown fumes of Br2, colourless SO2. Acid-base of HBr (same equation as general). Oxidation of Br-, 2Br- + H2SO4 + 2H+ -> Br2 + SO2 + 2H2O. Sulphuric acid reduction for SO2, 2H+ + 2Br- + H2SO4(l) -> SO2(g) + 2H2O(l) + Br2(l).
Drops of sulfuric acid are added to sodium IODIDE, what are the products? What type of reactions are these and what are the equations?
Steamy fumes of sodium iodide, black solid of iodine, bad egg smell of hydrogen sulphide, yellow solid sulphur. Hydrogen iodide is an acid-base reaction. SO2, S and hydrogen sulphide are reduced by iodide ions, 8H+ + 8I- + H2SO4(l) -> H2S(g) + 4H2O(l) + 4I2(s).
How else can we identify the halides?
Using their reactions with silver ions.
What are the steps to identifying a halide with silver ions?
Dilute nitric acid is added to the halide to remove any soluble carbonate or hydroxide impurities. A few drops of silver nitrate is added and a precipitate forms.
How would carbonate or hydroxide impurities interfere with the test for identifying halides using silver ions.
By forming insoluble silver carbonate or insoluble silver hydroxide.
For silver fluoride what precipitate do we see?
None.
For silver chloride what precipitate can we see? What happens dilute ammonia is added?
White precipitate, dissolves.
For silver bromide what precipitate do we see? How does it interact with dilute and conc. ammonia?
Cream precipitate, dissolves in conc. ammonia.
For silver iodide what precipitate do we see? What happens when dilute or conc. ammonia is added?
Pale yellow precipitate, doesn’t dissolve in either ammonias.
Why doesn’t fluorine form a precipitate?
It’s soluble in water.
What is the general equation for an acid-base reaction?
NaX(s) + H2SO4(l) -> NaHSO4(s) + HX(g)
What is the general equation for silver nitrate added to an acidified solution to test for a halide?
AgNO3(aq) + NaX(aq) -> NaNO3(aq) + AgX(s).
What do we use chlorine to do, why?
Treat drinking water and swimming pools, kills bacteria by oxidation.
How does chlorine react with water, what sort of reaction is this and what does it produce? What is the equation?
Dissolves in a reversible reaction to produce chloric (I) acid, HClO and HCl. Cl2(g) + H2O(l) -> HCl(aq) _ HOCl(aq).
What sort of reaction is happening when chlorine dissolves in water, why?
Disproportionation, one Cl is being reduced and the other oxidised.
Define disproportionation.
Simultaneous oxidation and reduction of a species.
How does chlorine react with cold, dilute sodium hydroxide (an alkali). What does it produce, what is the equation? What sort of reaction is this another example of?
Produces sodium chlorate NaClO, Cl2(g) + 2NaOH(aq) -> NaCl(aq) + NaOCl (aq) + H2O(l). Disproportionation.
What is the equation when an aqueous solution of chlorine is left in the sunlight?
2Cl2(g) + 2H2O(l) -> 4HCl(aq) + O2(g)
Sodium bromide reacts with concentrated sulfuric acid, write an equation for this reaction of sodium bromide.
2NaBr + 2H2SO4 -> Na2SO4 + Br2 + SO2 + 2H2O
A colourless solution contains a mixture of sodium chloride and sodium bromide.
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.
Add silver nitrate to form ppts of AgCl and AgBr, AgNO3 + NaCl -> AgCl + NaNO3, AgNO3 + NaBr -> AgBr + NaNO3. Add excess of dilute ammonia to the mixture of ppts. The AgCl dissolves, AgCl + 2NH3 -> [Ag(NH3)2]+ + Cl-, filter off remaining AgBr ppt, wash to remove soluble compounds, dry to remove water.
Write an ionic equation for the reaction between chlorine and cold dilute sodium hydroxide solution.
Cl2 + 2HO- -> OCl- + Cl– + H2O
Chlorine gas is bubbled through a solution containing bromide ions. What would you observe?
Turns to orange solution.
Explain why chlorine has a lower boiling point than bromine.
Br is bigger than Cl, has more e-s. Cl2 has weaker VDW forces between molecules making it easier and requiring less energy to break/ boil.
Write an equation for the reaction between strontium chloride solution and sodium sulfate solution.
SrCl2(aq) + Na2SO4(aq) -> SrSO4(aq) + NaBr(aq)
Describe briefly how you could obtain strontium sulfate from a mixture of strontium carbonate and strontium sulfate.
Add nitric acid to mixture, filter.
Explain why drinking magnesium sulfate solution is effective in the treatment of barium poisoning.
Insoluble BaSO4 formed, removes barium ions as a ppt.
