7 Group 2 & 7 Flashcards
Trend in Atomic radium down G2
Increases
More shells
More Dist Less Attract
More shielding
Trend in First IE Grp2
Decreases
More shielding
More shells
More distance
Less attract
Easier to remove e
Trend in water reactivity g2
Increases
more reducing power
easier to donate e due to increased Ar
Equation of G2 metal and water
Mg + 2H2O –> Mg(OH)2 + H2
Equation of G2 metal and steam
Explain why products form
Mg + H2O (g) –> MgO + H2
not stable to produce hydroxide, thermal decomposition
Trend in MP G2
Decreases
Ar inceases
Less attraction between positive metal ions and delocalised e.
Strength of metallic bonds decrease
Trend in solubility of G2 OH
Mg sparingly Ba soluble
Explain why Mg OH2 is sparingly soluble and not just insoluble
Slightly alkaline solution indicating some OH ions are dissolved in water
Reactions between G2 and water observations
Amount of precipitate formed decreases down grp, all white ppt, fizzing in all.
Test for Mg2+ in MgCl2
Add NaOH solution.
White ppt forms.
Explain a use of magnesium.
Extract titanium from titanium chloride:
TiO2 + 2Cl2 + C → TiCl4 + CO2
TiCl4 (l) + 2Mg (s) → 2MgCl2 (s) + Ti (s)
Very difficult to extract titanium from its ores (TiO2).
Initially converted to the chloride, then reduced by magnesium.
Use of Mg OH
Constipation and Antacid as its slightly alkaline and doesn’t irritate oesophagus.
Use of Ca OH
Neutralise acidic soil
Ca(OH)2 (aq) +2HCl (aq) → 2H2O (l) + CaCl2 (aq)
Use of calcium Oxide/ Carbonate
Flue gas removal
CaCO3 (s) + SO2 (g) → CaSO3 (s) + CO2 (g)
CaO (s) + SO2 (g) → CaSO3 (s)
Use of barium sulphate?
barium meals, outline gut in x rays, insoluble so safe.
Trend in sulphate solubility
decreases
Mg sol
Bas insol
Use of barium chloride to test for sulphate ions?
Acidify with HCL white ppt produced.
Na F and Cl with Sulphuric Acid
Br and I first step
NaCl + H2SO4 > HCl + NaHSO4
Br and I second step with Sulphuric acid
H2SO4 + 2H+ + 2Br- > Br2 + SO2 + 2H2O
2HI (g) + H2SO4 (l) → I2 (g) + SO2 (g) + 2H2O (l)
I third and fourth step with Sulphuric acid
6HI (g) + H2SO4 (l) → 3I2 (g) + S (s) + 4H2O (l)
8HI (g) + H2SO4 (l) → 4I2 (g) + H2S (s) + 4H2O (l)
Test for SO42-
- Acidify with dilute HCl 2. Add BaCl
White precipitate of BaSO4
Test for I-
Acidify with dilute HNO3
2. Add AgNO3
3. (Add dilute NH3 followed by conc. NH3)
Yellow precipitate Insoluble in conc. NH3
Test for CO32-
Add dilute HCl
Effervescence Gas produced turns limewater cloudy
Test for Br-
Acidify with dilute HNO3
2. Add AgNO3
3. (Add dilute NH3 followed by conc. NH3)
Cream precipitate dissolves in conc. NH3 (NOT with dilute)
Test for Cl-
Acidify with dilute HNO3
2. Add AgNO3
3. (Add dilute NH3 followed by conc. NH3)
White precipitate dissolves in dilute NH3
Test for OH-
Damp red litmus paper
Turns from red to blue
Test for Mg2+
In separate test-tubes:
* Add dilute NaOH With OH-: white precipitate
- Add dilute H2SO4 With SO42-: nvc
Test for Sr2+
In separate test-tubes:
* Add dilute NaOH With OH-: nvc
- Add dilute H2SO4 With SO42-: white precipitate
Test for Ca2+
In separate test-tubes:
* Add dilute NaOH With OH-: white precipitate/ suspension
- Add dilute H2SO4 With SO42-: slight white precipitate
Test for Ba2+
In separate test-tubes:
* Add dilute NaOH With OH-: nvc
- Add dilute H2SO4 With SO42-: white precipitate
Test for NH4+
- Add NaOH
- Heat sample
- Hold damp red litmus paper at test tube mouth
litmus paper will turn from red to blue.
chlorine with water to form chloride ions and chlorate (I) ions
Cl2(g) + H2O(l) <-> HCl(aq) + HClO(aq)
reversible reaction, green solution formed showing presence of chlorine.
Disproportionation
(0 -> +1 in HClO)
(0-> -1 in HCl)
If Univ Ind is added, red first then bleached, protons then chlorate bleach
reaction of chlorine with water to form chloride ions and oxygen
sunlight green colour fades
colourless gas is produced
2Cl2(g) + 2H2O(l) -> 4HCl(aq) + O2(g)
chlorine (0-> -1)
oxygen (-2 -> 0)
reaction of chlorine with cold, dilute, aqueous NaOH and uses
Cl(g) + 2NaOH(aq) -> NaCl(aq) + NaClO(aq) + H2O(l)
- if water replaced by NaOH, the equilibrium is destroyed as the NaOH reacts with the acids formed.
- commercial preparation of bleach NaClO
- the chlorate (1) may decompose to form chloride and chlorate (V)
3ClO^-(aq) -> 2Cl^-(aq) + ClO3^-(aq)
- the reaction is slow at rtp but fast at 70˚C
- NaClO3^-(aq) is a powerful weed killer
Why do we use ammonia to test for halides?
What is used to test if a precipitate definitely contains a halide based on their ability to redissolve.
The type of reaction involving NaCl + H2SO4
Acid-base
The type of reaction involving NaI + H2SO4 then I- + H2SO4 and finally 8H+ + 8I- + H2SO4
Acid-base then Redox
The type of reaction involving NaBr + H2SO4 then Br- + H2SO4
Acid-base then Redox
