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109 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What is the trend in atomic radius down group 2? |
Increases |
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Why does atomic radius increase down group 2? |
Each atom gains an extra principal energy level of electrons, whose orbitals are located further from their nucleus |
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What is the trend in first ionisation energy down group 2? |
Decreases |
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Why does first ionisation energy decrease down group 2? |
Electron is easier to remove as electron is lost from higher energy principal level, with more shielding and electron lost further from nucleus. |
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What is the trend in melting point down group 2? |
Decreases except Mg |
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Why does melting point decrease down group 2? |
Metallic bonding is weaker as size of metal ion increases so less attraction between positive ions + delocalised electrons |
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What do group 2 metal ions form when they react with water? |
Metal hydroxide and hydrogen gas |
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Mg + H2O -> |
Reacts very slowly with cold water but readily with steam to form magnesium hydroxide |
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Ca / Sr / Ba + H2O -> |
React with cold water (increase vigour down group) -Calcium hydroxide -Strontium hydroxide -Barium hydroxide |
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Why does the reactivity of group 2 metals increase as you go down the group? |
It's successively easier to remove electrons to form 2+ ion as atomic radius results in a decrease in attractive force between outer electrons + nucleus |
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Why do the resulting solutions of group 2 metals with water have high pH? |
Hydroxide ions from the metal hydroxide but actually depends on solubility of metal hydroxide |
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How is the solubility of the metal hydroxide in group 2 measured? |
Grams per 100g |
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What does solubility depend on? |
Mass of solute Amount of water Temperature |
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What is the trend in solubility down group 2? |
Increases |
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Why does the metal hydroxide become more basic as you go down group 2? |
As solubility increases, so does the concentration of OH- ions in solution |
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M (OH)2 (s) + water <-> |
M2+ (aq) + 2OH- (aq) |
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How does solubility affect equilibrium? |
More soluble the metal hydroxide, the more equilibrium lies to the right |
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How does the position of equilibrium affect concentration and pH? |
More equilibrium lies to right, greater the hydroxide ion concentration and higher the pH |
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Chemical test for Mg2+/Ca2+ |
MgCl2 (aq)(colourless) + NaOH (aq) --> Mg(OH)2(s) + NaCl (aq) |
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What is a reaction between metal hydroxides and acids? |
Neutralisation |
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Acid + base -> |
Salt + water |
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What is a salt? |
A metal in the place of hydrogen in an acid e.g. BaCl2 |
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What is milk of magnesia and what are its uses? |
Suspension of magnesium hydroxide used in medicine as a laxative and to relieve indigestion |
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What is slaked lime and what are its uses? |
Calcium hydroxide, used to raise the pH of acidic soil |
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What is the solubility trend of sulphates? |
Decreases as you go down the group - opposite to hydroxides |
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Chemical test for SO4²- ions |
Na2SO4 (aq) + BaCl2 (aq) --> BaSO4 (s) + NaCl |
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How is barium used in medicine? |
Mixture with barium sulfate coats intestinal lining and barium absorbs radiation when x-rayed to highlight black/white contrast |
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Why can toxic barium be consumed? |
Ba2+ (aq) ions usually toxic but BaSO4 solubility so low that hardly any Ba2+ (aq) present in solution |
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How is titanium made? |
Extracted from ore then converted from titanium (IV) oxide to titanium (IV) chloride at 900°, then displaced from TiCl4 by a more reactive metal e.g. magnesium |
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What equation represents the displacement of titanium from TiCl4? |
TiCl4 (s) + 2Mg (s) ----> Ti(s) + 2MgCl2 (s) |
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What are the two most useful properties of titanium? |
Corrosion resistant and high strength to weight ratio |
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What are the two most useful properties of titanium? |
Corrosion resistant and high strength to weight ratio |
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What does titanium produce? |
Alloys for a variety of tools in aerospace, military, medical, industrial and sporting applications |
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What can calcium carbonate and calcium oxide do? |
To neutralise the acidic gas, sulfur dioxide SO2, that's present in flue gases |
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When is sulfur dioxide formed? |
When sulfur impurities are burned in fossil fuels |
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CaO(s) + SO2 (g) -> |
CaSO3 (s) (calcium sulfate) |
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What are the halogens? |
Elements in group 7 - halogen comes from the Greek words for salt-making |
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What is the trend in electronegativity down the halogens? |
Decreases |
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Why does electronegativity decrease down the group? |
Atomic radius and shielding both increase therefore there is a weaker attraction between the nucleus and bonding pair of electrons in a covalent bond |
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Why do Van Der Waals increase down the group? |
Size increases as there are more electrons |
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What is the trend in boiling point down the halogens? |
Halogens have simple molecular structures and down group molecules have more electrons so stronger Van Der Waals forces between molecules so more energy required to break |
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F2 |
Yellow gas BP : -188 |
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Cl2 |
Green gas BP : -35 |
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Br2 |
Orange liquid BP : 59 |
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I2 |
Grey solid (184) |
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How do halogens react? |
As oxidizing agents |
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X2 + 2e- --> |
2X- |
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What is the trend in oxidizing ability down the group? |
Decreases as atomic radius and shielding increases so reducing ability of halogen to gain an electron |
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What makes something a better oxidizing agent? |
The better it can gain electrons |
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Which type of reaction are halogen displacement reactions? |
Redox |
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What does a halogen form after acting as an oxidizing agent? |
Halide ion |
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Chlorine + Potassium bromide |
Orange-brown solution |
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Chlorine and potassium iodide |
Dark brown solution |
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Bromine and potassium chloride |
No reaction |
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Bromine and potassium iodide |
Dark brown solution |
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Iodine and potassium chloride |
No reaction |
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Iodine and potassium bromide |
No reaction |
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Iodine and potassium bromide |
No reaction |
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What can chlorine react with? |
Water and cold sodium hydroxide in disproportionation reactions. |
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Cl2 + H2O <--> |
2H+ + Cl- + ClO- |
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What is a disproportionation reaction? |
A reaction in which the same element is simultaneously oxidized and reduced |
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Why is chlorine used to purify water supplies? |
It is toxic to bacteria, some of which can cause disease so is beneficial to the population |
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Why is chlorine somewhat dangerous? |
Toxic to humans + associated w/ gas leaks in chlorination process + can form chlorinated hydrocarbons |
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Cl2 + 2NaOH --> |
NaCl + NaClO + H2O |
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What does household bleach commonly contain chlorate (I) ion, ClO-, in the form of? |
Sodium chlorate (I), NaOCl |
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What does household bleach commonly contain chlorate (I) ion, ClO-, in the form of? |
Sodium chlorate (I), NaOCl |
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How is sodium chlorate formed? |
When chlorine reacts with cold, aqueous sodium hydroxide |
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2NaOH (aq) + Cl2 --> |
NaClO (aq) + NaCl (aq) + H2O |
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What does the chlorate (I) ion behave as? |
An oxidizing agent by oxidizing the organic compounds in food stains, bacteria and dyes |
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What is the trend in reducing ability as you go down group 7? |
Increase (in ability to lose electrons) |
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Why does reducing ability increase down the group? |
Ionic radius increases, increasing the ability of the halide ion to lose an electron |
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What do the reactions of sodium halides with concentrated sulfuric acid demonstrate? |
The relative strengths of the halide ions as reducing agents |
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How do the reactions of sodium halides with concentrated sulfuric acid occur? |
Stage 1 : displacement Stage 2 : redox |
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NaX (s) + H2SO4 (l) ---> |
NaHSO4 (s) + HX (g) |
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How does sulfuric acid act in a reaction with sodium halides? |
An acid (proton donor) |
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What is the second stage of reactions of halides with concentrated sulfuric acid? |
With bromides and iodides, a redox reaction occurs between the concentrated sulfuric acid and halide ion in HX |
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Why do fluoride and chloride ions not undergo redox with H2SO4? |
They're not good enough reducing agents ( they don't want to give H2SO4 any electrons) - small Ionic radius so outer electrons not lost easily |
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Why will bromide ions reduce? |
Bromide ions are relatively large so electrons are lost easier so give electrons to H2SO4 |
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What do bromide ions reduce H2SO4 to? |
SO2 (g) only |
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2Br + H2SO4 + 2H+ --> |
BR2 + SO2 + 2H2O |
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SO2 |
Reduction product - choking gas |
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Br2 |
Oxidation product - orange-brown fumes/liquid |
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Why do iodide ions reduce well? |
Large ion so electrons are lost easily and given to H2SO4 |
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What do iodide ions reduce H2SO4 to? |
SO2 (g) S (s) and H2S (g) |
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6I- + H2SO4 + 6H+ ---> |
3I2 + S + 4H2O |
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3I2 |
Oxidation product - black solid / purple vapour |
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S |
Reducing product - yellow solid |
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8I- + H2SO4 + 8H+ ---> |
4I2 + H2S + 4H2O |
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4I2 |
Oxidation product - black solid / purple vapour |
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H2S |
Reduction product - gas with a bad egg smell |
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Fluoride |
HF ( misty white fumes ) None None |
Displacement product Oxidation product Reduction product |
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Chloride |
HCl (misty white fumes)
None
None |
Displacement product Oxidation product Reduction product |
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Bromide |
HBr (misty white fumes)
BR2 (orange-brown vapour/liquid)
SO2 |
Displacement product Oxidation product Reduction product |
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Iodide |
HI (misty white fumes)
I2 (black solid / purple vapour)
SO2 (choking gas) / S (yellow solid) / H2S (bad-egg smell) |
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How can halides be identified? |
By their reaction with acidified silver nitrate solution |
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AgNO3 (aq) + NaX (aq) -> |
AgX (s) + NaNO3 (aq) |
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Ag+ (aq) + X- (aq) --> |
AgX (s) |
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What is the exception to identifying halide ions? |
AgF - doesn't produce a precipitate as AgF is soluble |
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Ag+ (aq) + OH- (aq) --> |
AgOH (s) |
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2Ag+ (aq) + CO32- (aq) --> |
Ag2CO3 (s) |
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What will form if a test sample has any soluble carbonate or hydroxide impurities? |
A silver precipitate of silver hydroxide or silver carbonate on addition of silver nitrate |
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H+ (aq) + OH- (aq) --> |
H2O (l) |
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2H+ (aq) + CO3^2- (aq) --> |
H2O (l) + CO2 (g) |
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NaX (aq) + AgNO3 (aq) --> |
AgF (aq) colourless solution AgCl (s) white precipitate AgBr (s) cream precipitate AgI (s) yellow precipitate |
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What is NH3 used for? |
To tell the colours of the precipates apart |
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Addition of dilute NH3 (aq) |
AgCl (s) white ppt dissolves AgBr (s) cream ppt partially dissolves AgI (s) yellow ppt insoluble |
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Addition of conc NH3 (aq) |
AgCl (s) white ppt dissolves AgBr (s) cream ppt dissolves AgI (s) yellow ppt insoluble |
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What molecule treats indigestion? |
CaO |
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What is titanium extracted from? |
Ore vutile - TiO2 |
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