7 Group 2 & 7 Flashcards by Abdullah Albeedh

Trend in Atomic radium down G2

Increases
More shells
More Dist Less Attract
More shielding

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Trend in First IE Grp2

Decreases
More shielding
More shells
More distance
Less attract
Easier to remove e

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Trend in water reactivity g2

Increases
more reducing power
easier to donate e due to increased Ar

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Equation of G2 metal and water

Mg + 2H2O –> Mg(OH)2 + H2

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Equation of G2 metal and steam
Explain why products form

Mg + H2O (g) –> MgO + H2

not stable to produce hydroxide, thermal decomposition

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Trend in MP G2

Decreases
Ar inceases
Less attraction between positive metal ions and delocalised e.
Strength of metallic bonds decrease

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Trend in solubility of G2 OH

Mg sparingly Ba soluble

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Explain why Mg OH2 is sparingly soluble and not just insoluble

Slightly alkaline solution indicating some OH ions are dissolved in water

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Reactions between G2 and water observations

Amount of precipitate formed decreases down grp, all white ppt, fizzing in all.

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Test for Mg2+ in MgCl2

Add NaOH solution.
White ppt forms.

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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.

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Use of Mg OH

Constipation and Antacid as its slightly alkaline and doesn’t irritate oesophagus.

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Use of Ca OH

Neutralise acidic soil
Ca(OH)2 (aq) +2HCl (aq) → 2H2O (l) + CaCl2 (aq)

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Use of calcium Oxide/ Carbonate

Flue gas removal
CaCO3 (s) + SO2 (g) → CaSO3 (s) + CO2 (g)
CaO (s) + SO2 (g) → CaSO3 (s)

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Use of barium sulphate?

barium meals, outline gut in x rays, insoluble so safe.

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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+

1. Add NaOH 2. Heat sample 3. 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