3.8 Reactivity Trends Flashcards
Group 2 elements form …
2+ ions
Group 2 reactivity increases …
as you go down the group
Group 2 oxides have a pH of approximately…
10
Uses of group 2 compounds
Ca(OH)2 - neutralise acids in soil and Mg(OH)2 - as “antacids” in treating indigestion.
Halogen Trends in Boiling points.
Boiling point increases as you go down the group.
Explain the Boiling point trend in the Halogens
- More electrons, 2. Stronger London Forces, 3. More energy to break intermolecular forces, 4. Therefore boiling point increases as you go down the group.
Cl in cyclohexane.
Pale green
Br in cyclohexane
Orange
I in cyclohexane
Violet
Halogen reactivity trend
Reactivity decreases as you go down the group.
Explain the reactivity trend in the halogens
- Atomic radius increases, 2. More inner shells so nuclear shielding increases, 3. Less nuclear attraction to capture an electron from another species 4. Reactivity decreases.
Disproportionation
A redox reaction in which the same element is oxidised and reduced.
Disproportionation reactions with chlorine
Cl and Water, Cl and cold, dilute, aqueous NaOH.
Carbonate test
dilute nitric acid and test gas by bubbling through lime water - If CO2 is produced a carbonate is present.
Sulfate test
add BaNo3 if a white precipitate forms SO4 is present.
Halide test
Add AgNO3 then add cyclohexane as the colours of the different precipitates are difficult to tell apart.
Why is there a correct order to complete the 3 anion tests
1.CO3 there is no confusion - if CO2is given off there is a CO3 present. 2. SO4 If you complete this test with a carbonate you will get a white precipitate as well. 3. Halide test Ag reacts with CO3 and SO4 to create precipitates.
Test for ammonium
Add NaOH, Warm, test with moist litmus paper - turn paper blue.
