3.1.2 Group 2 Flashcards by Saffie Khan

What are group 2 elements sometimes called

Why

The alkaline earth metals

Their oxides + hydroxides are alkaline

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What block are group 2 metals in

What electrons are in their outer shell

S block

2s electrons in outer shell

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When does group 2 atomic radius increase

Why

Going down the group

Each element has extra shell

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What generally happens to melting points going down group
Why

What element is the exception
Why

Decrease
As as atoms get larger, the sea of delocalised electrons are further away from positive nuclei so strength of attraction gets smaller

Mg is exception
It’s lattice atom arrangement is different to other alkaline metals

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What do group 2 elements do in all their reactions

Lose their 2 outer electrons to form doubly positively charged ions

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What’s the 1st and 2nd IE Equations of any group 2 elememts

1st : M (g) -> M+ (g) + e-

2nd: M+(g) -> M2+ (g) + e-

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Why does it get easier to remove the 2 outer electrons in reactions going down the group

As they get further away from the nucleus

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What makes an element more reactive

The easier it is to remove electrons

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What reactions occur when group 2 elements react with water

Redox

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E.g of magnesium reacting with water

Calcium reacting with water

Mg(s) + 2H20(l) -> Mg(OH)2(aq) + H2(g)

Ca(s) + 2H2O(l) -> Ca(OH)2(aq) + H2(g)

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What does calcium produce when reacting with water

What’s this used for

Limewater (slaked lime)

Used to treat acidic soil by farmers

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What does magnesium produce when it reacts with water

What’s this used for

Milk of magnesia

Used as an antacid to treat indigestion

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What does magnesium reacts slowly and fast with

Reacts slowly with cold water

Reacts fast with steam

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What do all of the alkaline metal hydroxides look like

All white solids

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What is solubility of metal hydroxides like going down group 2

Solubilities increase

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What’s the pH of the hydroxide like if it’s more soluble

More soluble, the more OH- is released and the pH is higher

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How do you test for the sulfate ion

2 steps

Using BaCl2/Ba(NO3)2

Acidity with dilute HNO3(aq)/dilute HCl (aq)
Add Ba(NO3)2(aq)/BaCl2(aq)

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What will form if the SO4 2- ion is present

What’s the equation

A white ppt of BaSO4

Ba2+(aq) + SO4 2-(aq) -> BaSO4(s)

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What ions could interfere with the results of testing for sulfate ion, id it’s present

What’s the equation

CO3 2- ions would also produce a white pot with Ba2+

Ba2+(aq) + CO3 2-(aq) -> BaCO3(s)

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Why is the acidifying step in place when testing for sulfate ions

To safeguard against CO3 2- ions interfering

Acid will destroy the carbonate ion by producing CO2 gas

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What do group 2 metals form when they react with oxygen

Metal oxide

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What charge is the metal and oxygen in reactions with oxygen

Metal is 2-

Oxygen is 2+

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What does Mg burn with in oxygen

Brilliant white light

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What occurs in reactions with oxygen (R+O)

Oxidation of metal

Reduction of oxygen

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What reaction is when group 2 metals react with dilute acids

MASH Metal + Acid -> Salt + Hydrogen

What happens to the metal and H+ in the acid in reactions with dilute acids

Metal oxidised from 0 -> +2 | Acids reduced from +1 -> 0

What do group 2 metal oxides form when they react with water

Alkaline solutions of metal hydroxides

What metal only reacts very very slowly with water to form a metal hydroxide

Magnesium

What do reducing agents do

Donate/lose electrons

What are classed as reducing agents | Why

Halides | As they can lose electrons

General eq for halides acting as reducing agents

2X- -> X2 + 2e-

What’s the weakest reducing agent | Strongest oxidising agent

F- weakest reducing agent | F2 strongest oxidising agent

What’s the strongest reducing agent | Weakest oxidising agent

I- strongest reducing agent | I2 weakest oxidising agent

What’s the halide ion like going down a group

Halide ion increases in size so outer electrons are less strongly attracted by nucleus and so ions can lose electrons more readily Also increased shielding

If a halogen is a strong oxidising agent what’s its halide like

Halide will be a weak reducing agent

How can some halide ions be precipitated (2)

1. Acidification with dilute nitric acid HNO3(aq) | 2. Addition of silver nitrate solution AgNO3(aq)

Why is HNO3 used to acidify the sample when testing for halide ions

As it removes cons that could effect the result

If fluorine is produced what precipitate is there

None

If chlorine is produced what precipitate is there

White

If bromine is produced what precipitate is there

Cream

If iodine is produced what precipitate is there

Yellow

How can halides be further distinguished

By dilute, then concentrated ammonia (NH3)

What solution does AgCl form when it dissolves with dilute ammonia solution

A colourless solution

AgBr dissolves in concentrated ammonia solution but what is it insoluble in

Dilute ammonia

Ionic Equations of testing for halide ions with chloride, bromide and iodide

Ag+(aq) + Cl-(aq) -> AgCl(s) Ag+(aq) + Br-(aq) -> AgBr(s) Ag+(aq) + I-(aq) -> AgI(s)

How would u know if NaOH is present

Pungent smell | Turns red litmus paper blue

What 2 things in the sample could affect the results as they react with AgNO3(aq)to produce white ppts

``` Soluble carbonates (CO3 2-) Hydroxides OH- ```

When chlorine dissolves in water what does it form What’s the equation

A mixture of hydrochloric acid,HCl and chloric acid, HClO Cl2(g) + H2O(l) HCl(aq) + HClO(aq)

What’s the process called when chlorine dissolves in water what happens to the chlorine

Disproportionation Chlorine has been simultaneously oxidised (lost electrons) and reduced (gained electrons)

What does the presence of Cl2 and an equilibrium make the solution look What does addition of alkali (OH- ions) cause to happen

Pale green Adds water pushing the equilibrium to the right causing the green to fade

What happens if addition of acid (H+ ions) occurs when chlorine water dissolves in water

The green intensifies and Cl2 has can be emitted which is TOXIC

What’s an advantage of Cl2 in drinking water and swimming pools despite its toxicity

It’s dissolved in water in low concentrations to kill any bacteria

What is chloric acid (HClO) | What does it also do

It’s an oxidant agent and a bleach | Kills bacteria

What happens to blue litmus paper when testing for chlorine water

Blue litmus paper turns red (due to HCl), followed by white

Why does litmus paper go white if chlorine waters present

As HClO is a bleach

As chlorine isn’t very soluble in water, what can it easily be lost by

Evaporation

What’s the active ingredient in household bleach as well as an oxidising agent How is it produced

Sodium chlorate(l) (NaClO) Produced when chlorine reacts with cold, dilute sodium hydroxide

What’s the equation for chlorine reacting with sodium hydroxide What type of reaction is this

Cl2(g) + 2NaOH(aq) -> NaClO(aq) + NaCl(aq) + H2O(l) Disproportionation of chlorine

What can chlorine in tap water react with and do

Can react with methane (CH4) decaying vegetation and forming chlorinated hydrocarbons that are suspected carcinogens

What could we get if we didn’t chlorinate water | E.g

Waterborne diseases e.g typhoid, cholera

What are 2 alternatives to using Cl2 that aren’t as good

Ozone (O3) | UV light

3.1.2 Group 2 Flashcards

(61 cards)