Group 2 And 7 Flashcards by caitlin rombouts

Why are the group 2 metals placed in the s block?

-outermost/highest energy electron is in the s orbital

How well did you know this?

Not at all

Perfectly

Why does melting point decrease down the group?

-ionic radius increases so ions become less charge dense
-weaker ESFA between cations and delocalised electrons

How well did you know this?

Not at all

Perfectly

Why does reactivity increase down Group 2

-In chemical reactions group 2 metals lose 2 electrons
-extra energy level every time so shielding and atomic radius increase
-weaker ESFA between nucleus and outermost e- so more easily lost

How well did you know this?

Not at all

Perfectly

What type of reaction is a group 2 metal with cold water?

-Redox

How well did you know this?

Not at all

Perfectly

State the equation for a group 2 metal and cold water

M + 2H2O -> M(OH)2 + H2

How well did you know this?

Not at all

Perfectly

What is magnesium hydroxide known as?

-milk of magnesia
-used in indigestion tablets to neutralise excess stomach acids

How well did you know this?

Not at all

Perfectly

What is calcium hydroxide known as?

-slaked lime
-used to reduce the acidity of soil

How well did you know this?

Not at all

Perfectly

Are group 2 reactions with steam more or less vigorous than those with cold water?

How well did you know this?

Not at all

Perfectly

What type of reaction is a group 2 metal with steam?

-Redox

How well did you know this?

Not at all

Perfectly

State the reaction of a group 2 metal with steam

M(s) + H2O (g) -> MO(s) + H2(g)

How well did you know this?

Not at all

Perfectly

What colour are all the insoluble group 2 hydroxides?

White

How well did you know this?

Not at all

Perfectly

The solubility of group 2 hydroxides…

Increase down the group

How well did you know this?

Not at all

Perfectly

Mg(OH)2 is almost…

Insoluble and may be sold as a suspension in water

How well did you know this?

Not at all

Perfectly

Ca(OH)2 is sparingly…

Soluble and may be sold in solution as limewater

How well did you know this?

Not at all

Perfectly

What is the formula for limewater?

Ca(OH)2

How well did you know this?

Not at all

Perfectly

What colour are the insoluble group 2 sulphates?

White

How well did you know this?

Not at all

Perfectly

How does solubility of the group 2 sulphates change down the group?

Decrease

How well did you know this?

Not at all

Perfectly

What is barium sulphate known as?

A barium meal

How well did you know this?

Not at all

Perfectly

Why is it safe to ingest barium sulphate despite it being highly toxic?

Because it is so insoluble

How well did you know this?

Not at all

Perfectly

What is barium meal used for?

To outline the gut in medical x rays

How well did you know this?

Not at all

Perfectly

What else can barium sulphate be used for?

-to test the presence of sulphate ions in an unknown sample

How well did you know this?

Not at all

Perfectly

Why is a solution acidified with nitric or hydrochloric acid before testing for sulphate ions?

-to get rid of any carbonate ions that may interfere with the experiment
-barium carbonate would be formed

How well did you know this?

Not at all

Perfectly

What do you do after you acidify the solution to test for sulphate ions?

-add barium chloride
-if a white precipitate (BaSO4) forms that’s means sulphate ions are present

How well did you know this?

Not at all

Perfectly

What is the ionic equation for barium and sulphate ions?

Ba2+ + SO42- -? BaSO4

How well did you know this?

Not at all

Perfectly

What else can magnesium be used for?

-Production of titanium

How is titanium extracted?

-titanium ore is converted to titanium chloride which is then reduced to titanium by reaction w/ magnesium

State the equation for reduction of titanium chloride using magnesium

TiCl4 + 2Mg -> Ti + 2MgCL2

What can calcium oxide to be used for?

Flue gas desulfurisation

What type of reaction is CaO with SO2?

Acid-base

Before flue-gases are released into the atmosphere they are…

Scrubbed with calcium oxide

State the reaction of calcium oxide with sulfur dioxide?

CaO + SO2 -> CaSO3

What type of structure do halogens have?

Simple molecular structure

What is electronegativity?

The ability of an atom to withdraw e- density towards itself in a covalent bond

How does electronegativity change down the group?

-decreases -extra energy level each time so shielding and atomic radius increase -weaker ESFA between nuclear and bonding electrons

The combination of reagents required to test for halide ions is:

(I) dilute nitric acid (II)silver nitrate (AgNO3)

What is the purpose of dilute nitric acid in the tests for halide ions?

-to get rid of impurities such as carbonate -carbonate would cause fizzing

When are the precipitates formed in a test for halide ions using silver nitrate?

-When aqueous Ag+ reacts with an aqueous halide ion X- to form a solid silver halid, AgX Ag+ + X- -> AgX(s)

What silver halide does not form a precipitate as it is soluble?

Silver Fluoride AgF

What is the white silver halide precipitate?

AgCl

What is the cream silver halide precipitate?

AgBr

What is the yellow silver halide precipitate?

AgI

What is the only silver halide precipitate that dissolves in dilute ammonia

AgCl

What is the equation of the reaction with silver chloride and ammonia?

AgCl + 2NH3 -> [Ag(NH3)2]+ + Cl-

What is [Ag(NH3)2]+

-a silver complex present in toluene’s reagent -silver ion with two ammonia molecules in a linear arrangement -lone pairs on N atoms in the ammonia molecules form dative covalent bonds with silver ion in the centre

How do you differentiate between AgBr and AgI

-add concentrated ammonia -AgBr dissolves and AgI doesn’t

What is the equation for the dissolving of AgBr?

AgBr (s) + 2NH3 -> [Ag(NH3)2] + Br-

What is the trend in solubility of the silver halide down the group?

-decreases down the group

What is oxidising power?

-ability to gain electrons

Do halides or halogens have oxidising power

Halogens

What is halogen displacement?

-when a more reactive halogen displaces a less reactive halogen from a solution of one of its salts

What happens when Cl2 reacts with KBr

-colourless to orange (Cl2 is a pale green solution)

What colour change happens when Cl2 is added to Ki

Colourless to brown

What colour change happens when Br2 is added to potassium iodide?

-colourless to brown (Br2 is an orange solution)

State the overall and ionic equation for Chlorine and potassium bromine

-Cl2 + 2Kbr -> 2KCl + Br2 -Cl2- + 2Br -> 2Cl- + Br2

What is the strongest oxidising agent?

Cl2 as it can displace Br2 and I2

How does oxidising power change down the group

Decreases

why does oxidising power change down the group?

X2 + 2e- -> 2x- -extra energy level each time - increase in atomic radius and shielding -weaker ESFA between nucleus and incoming electron so its harder to gain a electron

How are relative oxidising or reducing powers of species quantified?

Using standard electrode potentials

The more positive the value on the SEP the more feasible the…

Reduction process is

What is the strongest oxidising agent?

What is the weakest oxidising agent?

What is the strongest reducing agent?

I-

What is the weakest reducing agent?

F-

What is reducing power?

-the ability to reduce -ability to be oxidised

When we are looking at reducing power we look at the ease with which the following process occurs:

2X- -> X2 + 2e-

How does reducing power change down the group?

Increases

What happens where KCL is added to H2SO4

Observations: -white fumes -effervesence HCl

What is the equation for KCl and H2SO4

H2SO4 + KCl -> KHSO4 + HCl

Is the reaction between sulphuric acid and potassium chloride redox?

No -no change in oxidation state ‘Cl- will not reduce H2SO4’ This is an acid-base reaction

What happens when you add KBr to H2SO4

-White fumes (HBr) -Effervesence (SO2) (choking gas) -orange vapour (Br2)

How many equations are there for the reaction between KBr and H2SO4

2 -redox -acid base

What is the acid base reaction between H2SO4 and KBr

H2SO4 + KBr -> KHSO4 + HBr

What does a reaction between H2SO4 and KBr produce?

HBr Br2 (redox) SO2 (redox)

Why is Br- and better reducing agent than Cl-?

As there is a redox reaction with conc H2SO4

What observations are there when KI is added to H2SO4

-effervesence (choking gas) (SO2) -white fumes (HI) -yellow solid (S) -black solid (I2) -rotten egg smell (H2S)

Whart is the Acid-base reaction when potassium iodide is added to sulphuric acid?

KI + H2SO4 -> KHSO4 + HI

Why do we know iodide is the most powerful reducing agent?

-I- can reduce S in H2SO4 from +6 down to +4 (in SO2,) 0 (in S) and -2 (in H2S)

Why does reducing power of the halides change down the group?

-ionic radius increases (extra energy level each time) -shielding increases -weaker ESFA between nucleus and outer e- -e- lost more easily

What happens when Cl2 is bubbled into water?

-A pale green solution is formed

What is the equation for when chlorine is bubbled into water?

Cl2 + H2O <—> HCl + HClO

What is HClO?

Chloric (I) acid

What type of reaction is the reaction of Cl2 with H2O?

Disproportional reaction

What happens in a disproportionate reaction?

When one species is simultaneously oxidised and reduced

ClO- is a powerful…

Bleach

Where does the reaction of Cl2 with H2O take place?

-swimming pools and drinking water -ClO- is an oxidising agent that kills bacteria

Why is chlorine still ok to treat water despite it being toxic?

-only used in small amounts -health benefits outweigh the risk

Rewrite Cl2 + H2O <—> HCl + HClO

Cl2 + H2O <—> 2H+ + Cl- + ClO-

What happens to the yield of ClO- ions if acid (H+) is added? Cl2 + H2O <--> 2H+ + Cl- + ClO-

-Le Chateliers principle -Reaction works to remove added H+ -Backwards reaction favoured -POE moves to left -Yield of ClO- decreases

Using Le Chateliers principle, how would the system rep one if NaOH was added? Cl2 + H2O <--> 2H+ + Cl- + ClO-

-When OH- is added, OH- reacts w/ H+ ions, removing them -Reaction works to replace lost H+ -forwards reaction favoured -POE moves to RHS -yield of ClO- increases

Why is NaOH added to swimming pools?

-OH reacts with H+ -Forwards reaction favoured -More ClO- -More bacteria killed

What is the reaction that takes place when NaOH is added to chlorine?

Cl2 + 2NaOH -> NaCl + NaClO + H2O

What is the reaction of Cl2 with H2O in the presence of sunlight?

2Cl2 + 2H2O -> 4HCl + O2

Why do outdoor swimming pools require more frequent additions of chlorine

-Chlorine is lost from swimming pools

What is an alternative to the direct chlorination of swimming pools?

-Add sodium chlorate -Dissolves in water to form chloric acid NaClO + H2O -> NaOH + HCLO

Why do pools that are treated with Sodium Chlorate require a pH less than 7?

-H+ reacts with OH- (in NaOH) removing OH- reaction works to replace lost OH- -forward reaction favoured -P.o.E moves to RHS -increased yield of HCLO (CLO- kills bacteria)

What is NaCLO?

Sodium Chlorate