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Group 2 and 7

AQA A Level Chemistry

QuestionAnswer
"Why are elements in Group I (alkali metals) and Group II (alkaline earths) known as s-block elements ? their highest energy (bonding) electrons are in s orbitals.
Why does atomic radius increase down group 2? "the greater the atomic number the more electrons there are; these go into shells increasingly further from the nucleus
Why does melting point decrease down group 2? "each atom contributes two electrons to the delocalised cloud, metallic bonding gets weaker due to increased size of ion, Larger ions mean that the electron cloud doesn’t bind them as strongly
Why does first ionisation energy decrease down group 2? Despite the increasing nuclear charge the values decrease due to the, extra shielding provided by additional filled inner energy levels
Why is the second ionisation energy of Magnesium higher than the first ionisation energy? There are now 12 protons and only 11 electrons. The increased ratio of protons to electrons means that it is harder to pull an electron out
Why is there such a big jump between the 2nd ionisation energy and the 3rd Ionisation energy of Magnesium? Because the electron being removed is from a shell nearer the nucleus; there is less shielding
Write an balanced equation with state symbols for the reaction of Magnesium with steam. "Mg (s) + H2O (g) → MgO (s) + H2 (g)
Write an balanced equation with state symbols for the reaction of Barium water Ba (s) + 2H2O (l) → Ba(OH)2 (aq) + H2 (g)
What is the trend in solubility of the Group 2 Hydroxides? They get more soluble down the group.
Why do the group 2 metals get more reactive as you go down the group? Reactivity of metals is related to their ionisation energy. The ionisation energies of metals decreases down the group due to increased shielding and increased distance from the nucleus to the outer shell
What is the trend in solubility of the Group 2 Sulphates? They get less soluble down the group.
Why is calcium hydroxide more soluble than magnesium hydroxide and more strongly alkaline? "Lower charge density of the larger Ca2+ ion means that it doesn’t hold onto the OH¯ ions as strongly. More OH¯ get released into the water. It is more soluble and the solution has a larger pH.
Describe the chemical test for sulfate ions Use barium chloride in the presence of dilute hydrochloric acid. This will produce a white precipitate if sulfate ions are present.
Write an ionic equation with state symbols for the reaction in the sulfate test. Ba2+ (aq) + SO42– (aq) → BaSO4 (s)
Write a balanced equation with state symbols for the combustion of Barium in air. 2Ba (s) + O2 (g) → 2BaO (s)
Write a balanced equation with state symbols for the reaction of calcium with sulfuric acid Ca + H2SO4 →CaSO4 + H2
Write a balanced equation with state symbols for the reaction of strontium with nitric acid Sr + 2HNO3 → Sr(NO3)2 + H2
Why does the boiling point of Group 7 elements increase down the group? " increased number of electrons in larger atoms, the van der waals forces between molecules increase so more energy is required to separate the molecules
Why does the atomic radius of the Group 7 elements increase down the group? "the greater the atomic number the more electrons there are, these go into shells increasingly further from the nucleus
Why does the electronegativity of the Group 7 elements decrease down the group? "There is an increasing number of shells so more shielding and less pull on the outer electrons and an increasing atomic radius so attraction of nucleus for outer electrons drops off as distance increases
What is the trend in oxidising power of Group 7 elements down the group? It decreases
Why does the oxidising power of Group 7 elements decrease down the group? "the increasing nuclear charge which should attract electrons more is offset by INCREASED SHIELDING and INCREASING ATOMIC RADIUS
Write a balanced chemical equation with state symbols for the reaction of Chlorine with Sodium Bromide "Cl2(aq) + 2NaBr(aq) ——> Br2(aq) + 2NaCl(aq)
Write an balanced ionic equation for the reaction of Bromine with Iodide ions. "Br2 + 2I¯ ——> I2 + 2Br¯
What observation would be made with bromine is reacted with sodium chloride? "Solution goes from colourless to orange-red
What observation would be made with chlorine is reacted with sodium iodide? No visible reaction.
What observation would be made when solid sodium chloride reacts with concentrated sulfuric acid. Steamy Fumes
What a balanced equation for when solid sodium chloride reacts with concentrated sulfuric acid. "NaCl + H2SO4 → NaHSO4 + HCl
Write down three observations that would be made when sodium bromide reacts with concentrated sulfuric acid. steamy fumes, brown fumes, a colourless gas
Name the three gases produced that would be made when sodium bromide reacts with concentrated sulfuric acid. Hydrogen Bromide, Bromine and Sulfur Dioxide.
Write two ionic equations that show the formation of the three gases formed when sodium bromide reacts with concentrated sulfuric acid. H+ + Br- → HBr and H2SO4 + 2 H+ + 2 Br- → Br2 + SO2 + 2 H2O
Write down five observations that would be made when sodium iodide reacts with concentrated sulfuric acid. White fumes, Orange fumes, Colourless gas, Yellow solid, Bad Egg Smell
Name the three gases produced when sodium Iodide reacts with concentrated sulfuric acid. "Hydrogen Iodide, Iodine, Sulfur Dioxide, Sulfur, Hydrogen Sulfide
Write an ionic equation that shows the formation of Iodine and Sulfur Dioxide when sodium iodide reacts with concentrated sulfuric acid. H+ + I- → HI
Write an ionic equation that shows the formation of iodine and sulfur dioxide when sodium iodide reacts with concentrated sulfuric acid. H2SO4 + 2 H+ + 2 I- → I2 + SO2 + 2 H2O
Write an ionic equation that shows the formation of iodine and sulfur when sodium iodide reacts with concentrated sulfuric acid. H2SO4 + 6 H+ + 6 I- → 3 I2 + S + 4 H2O
Write an ionic equation that shows the formation of iodine and Hydrogen Sulfide when sodium iodide reacts with concentrated sulfuric acid. H2SO4 + 8 H+ + 8 I- → 4 I2 + H2S + 4 H2O
Explain why the ability of halide ions to acts as reducing agents increases down the group. "Down the group it becomes easier to lose an electron because ions are larger & there is more shielding (due to extra electron shell)
List the four steps for testing an unknown solution for halide ions "acidify with dilute nitric acid, add a few drops of silver nitrate solution, treat any precipitate with dilute ammonia solution, if a precipitate still exists, add concentrated ammonia solution
What is observation for a positive result to show the presence of chloride ions? white ppt soluble in dilute ammonia
What is observation for a positive result to show the presence of bromide ions? "cream ppt insoluble in dilute ammonia but soluble in conc.
What is observation for a positive result to show the presence of iodide ions? "yellow ppt insoluble in dilute and conc. ammonia solution
Write an ionic equation with state symbols for the formation of silver fluoride "Ag+(aq) + F¯(aq) ——> AgF (s)
Write an equation with state symbols for the reactions of chlorine with water Cl2(g) + H2O(l) <——> HCl(aq) + HOCl(aq)
Why is the reaction of chlorine with water called a DISPROPORTIONATION reaction? Because chlorine is simultaneously oxidised and reduced.
What is the chemical test for chlorine? "Blue litmus will be turned red then decolourised in chlorine water
Write a balanced chemical equation with state symbols for the reaction of Chlorine with cold aqueous sodium hydroxide 2NaOH(aq) + Cl2(g) —> NaCl(aq) + NaOCl(aq) + H2O(l)
Explain in terms of the changes in oxidation number why the reaction of Chlorine and cold aqueous sodium hydoride is an example of a DISPROPORTIONATION reaction. Chlorine changes from 0 to -1 and 0 to +1 in the same reaction.
Created by: JBearfield
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