Group 2 and Group 7

for group 2 metals, reactivity - down the group

increases

for group 2 metals, m.p. and b.p. - down the group

decrease

describe: magnesium reaction with cold water

very slow, white precipitate forms

describe: calcium reaction with cold water

fizzing, fairly vigorous, cloudy precipitate forms

describe: strontium reaction with cold water

vigorous reaction

describe: barium reaction with cold water

vigorous reaction

describe: magnesium reaction with steam

quick reaction, white powder forms

equation for magnesium + cold water

Mg(s) + 2H2O(l) → Mg(OH)2(s) + H2(g)

equation for calcium + cold water

Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)

equation for strontium + cold water

Sr(s) + 2H2O(l) → Sr(OH)2(aq) + H2(g)

equation for barium + cold water

Ba(s) + 2H2O(l) → Ba(OH)2(aq) + H2(g)

group 2 hydroxides - in solubility down the group

increase

equation for magnesium + steam

Mg(s) + H2O(g) → MgO(s) + H2(g)

what is Mg(OH)2 used for

antacids; acid indigestion medication

what is Ca(OH)2 used for

to make solid slaked lime to neutralise acidic soil

ionic equation for magnesium + sulfate compound

Mg^2+(aq) + SO4^2-(aq) → MgSO4(aq)

ionic equation for calcium + sulfate compound

Ca^2+(aq) + SO4^2-(aq) → CaSO4(s)

ionic equation for strontium + sulfate compound

Sr^2+(aq) + SO4^2-(aq) → SrSO4(s)

ionic equation for barium + sulfate compound

Ba^2+(aq) + SO4^2-(aq) → BaSO4(s)

group 2 sulfates - in solubility down the group

decrease

why is BaSO4 not harmful when used as barium meal

it is insoluble

what is BaSO4 used for

taken as barium meal to outline the gut in medical X-rays

what is BaCl2 used for

to test for sulfate ions in solution

what two things should you add to a solution to test for sulfate ions

nitric acid, BaCl2

what is the positive test for sulfate ions in a solution (testing with BaCl2)

white precipitate forms

why should you add nitric acid to the solution you’re testing for sulfate ions BEFORE you add BaCl2

to remove any carbonate ions (as CO2) that would also react with barium to form a white precipitate

for group 7 halogens, electronegativity - down the group

decreases

for group 7 halogens, mp and bp - down the group

increase

for group 7 halogens, reactivity - down the group

decreases

for group 7 halogens, ability as oxidising agents - down the group

decrease

for halides, reducing abilities - down the group

increase

fluorine appearance at room temperature

pale yellow gas

chlorine appearance at room temperature

greenish gas

bromine appearance at room temperature

red-brown liquid

iodine appearance at room temperature

black solid

what kind of reaction is sodium chloride + sulfuric acid

acid-base

observations for sulfuric acid + solid NaCl

fumes of HCl

why is HF(g) dangerous

it will etch glass

equation for sodium chloride + sulfuric acid

NaCl(s) + H2SO4(aq) → NaHSO4(s) + HCl(g)

observations for sodium bromide + sulfuric acid

steamy fumes of HBr, brown fumes of Br2, colourless sulfur dioxide with pungent odour produced

what kind of reaction is the first half of the reaction for sodium bromide + sulfuric acid

acid base

what kind of reaction is the second half of the reaction for sodium bromide + sulfuric acid

redox

equation for the first reaction (acid base reaction) between sodium bromide and sulfuric acid

NaBr(s) + H2SO4(l) → NaHSO4(s) + HBr(g)

equation for the second reaction (redox reaction) between sodium bromide and sulfuric acid

2HBr(g) + H2SO4(aq) → SO2(g) + Br2(aq) + 2H2O(l)

observations for sodium iodide + sulfuric acid

steamy fumes of HI(g) produced, black solid iodine, bad egg smell of H2S(g)

what kind of reaction is the first half of the reaction for sodium iodide + sulfuric acid

acid base

what kind of reaction is the second half of the reaction for sodium iodide + sulfuric acid

redox

equation for first reaction (acid-base) for sodium iodide + sulfuric acid

NaI(s) + H2SO4(l) → NaHSO4(s) + HI(g)

equation for second reaction (redox) for sodium iodide + sulfuric acid

8HI(g) + H2SO4(aq) → H2S(g) + 4H2O(l) + 4I2(s)

reaction of chlorine and water

Cl2(g) + H2O(l) → HClO(aq) + HCl(aq)

2 terms to describe the reaction between chlorine and water

disproportionation, reversible

how does HClO kill bacteria

via oxidation

reaction with chlorine + water in sunlight

2Cl2(g) + 2H2O(l) → 4HCl(aq) + O2(g)

what is the alternative to directly chlorinating pools with chlorine

adding NaClO(s)

give the equation for the reversible reaction between sodium chlorate + water

NaClO(s) + H2O(l) → NaOH(aq) + HClO(aq)

why must pools be kept slightly acidic if they are chlorinated using sodium chlorate instead of chlorine

in alkaline solutions, the equilibrium for the reversible reaction between sodium chlorate and water will move to the left, reducing the number of chloride ions present

why add nitric acid before adding silver nitrate solution in the test for halide ions

to get rid of any carbonate or hydroxide ion imurities which would form Ag2CO3 or AgOH precipitates