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Chemistry > 8 Reactivity Trends > Flashcards

8 Reactivity Trends Flashcards

1
Q

What is the trend in reactivity down group 2?

A

More reactive down group

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2
Q

Why does reactivity change down group 2?

A

More shells, bigger atomic radius
More shielding, weaker nuclear attraction all outweighs greater nuclear charge
So first and second ionisation energy decrease down group so less energy to form 2+ ion down group there fore more reactive

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3
Q

What is the trend in solubility down group 2 hydroxides?

A

More soluble down group 2

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4
Q

What does magnesium hydroxide look like in aqueous soloution and why?

A

Slight white precipitate as only slightly soluble in water

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5
Q

What does Barium hydroxide look like In aqueous soloution and why?

A

Colourless, soluble In water

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6
Q

What is the trend in alkalinity in group 2 hydroxides and why?

A

More soluble down group so greater OH- concs so more alkaline down group

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7
Q

What is calcium hydroxide used for?

A

Neutralises acidic soil

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8
Q

What group 2 compounds can be used to treat indigestion? And why?

A

Mg(OH)2 (milk of magnesia), CaCO3

Used as bases to neutralise HCL in stomach

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9
Q

Method for experiment to show trend in solubility and alkalinity of hydroxide?

A

Add spatula or metal oxides In water test tube and shake
Not much water so saturated solution therefore precipitate of hydroxides in tube
Measure PH of soloution w litmus paper
Alkalinity (and solubility) increases down group

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10
Q

Explain the trend in BP of halogens?

A

More electrons down group
Greater London forces
More energy to overcome forces
Increased BP down group

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11
Q

Appearance of F2 at RTP

A

Pale yellow gas

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12
Q

Appearance of Cl2 at RTP

A

Pale green gas

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13
Q

Appearance of Br2 at RTP

A

Brown liquid

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14
Q

Appearance of I2 at RTP

A

Grey black solid

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15
Q

Appearance of At2 at RTP?

A

Not seen

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16
Q

Appearance of Cl2 in H20?

A

Pale green liquid

17
Q

Appearance of Br2 in H20?

A

Orange liquid

18
Q

Appearance of I2 in H20?

A

Brown liquid

19
Q

Appearance of Br2 in Cyclo hexane?

A

Orange liquid

20
Q

Appearance of Cl2 in Cyclohexane?

A

Pale green liquid

21
Q

Appearance of I2 in cyclohexane?

A

Violet liquid

22
Q

Why do we add cyclohexane to halogens?

A

To distinguish between Br2 and I2 as they look similar in water, I2 is violet in cyclo hexane

23
Q

Explain the trend in reactivity in halogens?

A

Down group there is
Bigger atomic radius,more shells,more shield
Ing ( this outweighs increase nuclear charge)
So nuclear attraction decreases down group
Therefore harder to gain an electron to become an X- ion down group
So less reactive down group

24
Q

What is a disproportionate on reaction

A

Same element is simultaneously oxidised and reduced

25
Q

What is the reaction between Cl2 and H20? W names of products ?

A

Cl2 + H20 makes HCl + HClO
Hydrochloric acid
Chloric(I) acid

26
Q

What does chloric acid do?

A

Kill a bacteria

Acts as a weak bleach

27
Q

How do we demonstrate chloric acids bleaching ability?

A

Add indicator to chlorine in water

Turns red bc acidic and then goes colourless as is bleached

28
Q

What do we react Cl2 with to get concentrated bleach?

A

Cold dilute aqueous NaOH

29
Q

Why do we get concentrated bleach from Cl2 in NaOH and not water ?

A

Cl2 not very soluble in water so low conc of Chlorate(I) ions formed

30
Q

Write equation for Cl2 in cold dilute aqueous NaOH

A

Cl2 + 2NaOH makes Nacl + NaClO +H20

31
Q

Why is chlorine dangerous ?

A

Chlorine gas is very toxic

32
Q

How do u test for carbonate? Reagent,equation,positive result

A

Dilute nitric acid
CO3^2- (aq) + 2HNO3 (aq) -> H20(l) + CO2 (g) + NO3^-
Positive test: effervescence

33
Q

How do u prove the gas from carbonate test is CO2? (W equation)

A

Bubble through like water (Ca(OH)2) will turn cloudy

Ca(OH)2 + CO2 -> CaCO3 (s) + H20

34
Q

How do u test for sulfates? Reagent,equation,positive result

A

Ba(NO3)2
Ba (aq) + SO4^2- -> BaSO4 (s)
Positive : white ppt

35
Q

How do u test for a halide ? Reagent,equation,positive result

A 
AgNO3
Ag^+1(aq) + X^-1 (aq) -> AgX (s)
Positive:
AgCl white ppt
AgBr cream ppt
AgI yellow
36
Q

Further test to distinguish Silver halides?

A

AgCl dissolves in dilute NH3
AgBr dissolves in conc NH3
AgI insoluble in NH3

37
Q

What sequence do we do tests in and why?

A

Carbonate then sulphate then halide
-first use up all carbonate ions if present so no BaCo3 white precipitate
-then use all sulfate ions present so no Ag2SO4 or Ag2CO3 as both are white precipitates
Eliminates false positives

38
Q

Test for ammonium ion

A

Warm NaOH
NH4^+1 (aq) + OH^-1 (aq) -> NH3 (g) + H20 (l)
Will smell, test w indicator paper will go blue bc alkaline gas

Chemistry (17 decks)

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