topic 4 Flashcards by Saru B

What is a common name given to group 2 metals?

Alkaline earth metals

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What is the most reactive metal of Group 2?

Barium

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List 3 physical properties of group 2 metals?

High melting and boiling points
Low density metals
Form white compounds

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The highest energy electrons of Group 2 metals are in which subshell?

S subshell

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What is the trend in reactivity down group 2? Why is it this way?

it increases down the group
Electrons are lost more easily due to larger atomic radius and increased shielding

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What is the trend in ionisation energy down group 2? Why is it this way?

it decreases
increased number of shells, so more shielding
increased atomic radius, so weaker forces of attraction to nucleus
so less energy is needed to remove electron

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What type of reaction is the reaction between group 2 elements and oxygen?

redox reaction

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What are the products when group 2 elements react with water?

hydroxide (OH-)
hydrogen gas (H2)

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Which group 2 element does not react with water?

Beryllium

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Which group 2 element reacts very slowly with water?

magnesium

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What type of reaction is the reaction between group 2 metals and water?

Redox reaction

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What are the products when a group 2 oxide reacts with a dilute acid?

salt
water

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What is formed when group 2 oxides react with water?

metal hydroxide

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What is the trend in hydroxide solubility down group 2?

increases down the group
Mg(OH)2 is slightly soluble
Ba(OH)2 creates a strong alkaline solution

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Which group 2 metal oxide is insoluble in water?

Beryllium oxide

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what is the trend of sulfate solubility down group 2

become less soluble down the group

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What is the reasoning behind the trend in thermal stability for Group 1 carbonates and nitrates?

they do not decompose except for lithium
they dont have big enough charge densities to polarise the carbonate ion as they only form 1+ ions
lithium ion is just small enough to have the polarising effect so it can decompose

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What is the reasoning behind the trend in thermal stability for Group 2 carbonates and nitrates?

more thermally stable as you go down the group
cations get bigger so have less of a polarising effect (distort the carbonate/nitrate ion less)
C-O/N-O bond not weakened as much and therefore it is harder to break down

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List the flame colours for the group 1 elements?

Lithium = red
Sodium = orange/yellow
Potassium = lilac
Rubidium = red
Caesium = blue

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List the flame colours for Group 2 elements?

Magnesium = no colour
Calcium = brick red
Strontium = crimson red
Barium = pale green

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How do you carry out a flame test?

1) Nichrome wire
2) Sterilise it by dipping the into conc. HCl and then heating it in the Bunsen flame
3) Dip wire into solid and put in Bunsen flame and observe the flame

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How are the colours from the flame test formed?

The heat causes the electron to get excited and this move to a higher energy level but as this higher level the electron is unstable so then moves back down. As it moves from a higher energy level to a lower energy level, energy is emitted in the form of visible light energy which is the colour you see

What are the group 7 elements called?

Halogens

List 2 properties of halogens?

Low melting and boiling points
Exist as diatomic molecules

What is the trend in boiling points down group 7? Why is it this way?

increases down the group size of atom increases as more shells stronger London forces of attraction between molecules, take more energy to break

What is the trend in reactivity down group 7? Why?

it decreases atomic radius increases, electron shielding increases so ability to gain an electron and form 1- ions decreases

Explain the electronegativity trend down group 7?

it decreases down the group atomic radii increases (more shells) reduced nuclear attraction between electron and nucleus

What is the trend in oxidising ability down group 7? Why?

decreases down the group Cl has fewest occupied electron shells, so there are greater forces of attraction between outer electrons and nucleus, so it is easier to gain electrons and be reduced

What is the trend in reducing ability of the halides down the group? Why?

It increases down the group I- has most shells so outer electrons are further from nucleus, so weaker force of attraction between them, so it is he easiest to be oxidised and lose the electrons

What is a displacement reaction?

When a more reactive element displaces (replaces/pushes out) a less reactive element from a compound that contains the less reactive element.

What is the colour of chlorine in water?

Pale green

What is the colour of bromine in water?

Orange

What is the colour of iodine in water?

brown

What is the colour of chlorine in cyclohexane?

pale green

What is the colour of bromine in cyclohexane?

orange

What is the colour of iodine in cyclohexane?

violet

What is the equation for the reaction of Cl2 with water?

Cl2 (g) + H2O (l) —> HClO(aq) + HCl (aq)

Why is chlorine added to drinking water?

It kills the bacteria in the water and makes it safer to drink

What is the equation for forming bleach and conditions?

cold dilute alkali Cl2 (aq) +2NaOH(aq) —> NaCl(aq) + NaClO(aq) +H2O (l) NaClO is bleach

What do you use to test for halide ions?

Acidified AgNO3

Result and equation for AgNO3 with Cl- test?

white ppt Ag+ + Cl- —> AgCl(s)

Result and equation for AgNO3 with Br- test?

cream ppt Ag+ + Br- —> AgBr (s)

Result and equation for AgNO3 with I- test?

yellow ppt Ag+ + I- —> AgI(s)

results for silver halide precipitates when dilute/conc NH3 added?

AgCl dissolves in dilute and conc AgBr only dissolves in conc AgI will not dissolve in either

What products are formed when I- reduces H2SO4?

SO2 (choking gas) S (yellow solid) H2S (smells like rotten eggs) iodine gas (purple vapour) or iodine solid (black solid)

What are the products of Br- and H2SO4?

HBr + sulfuric acid -> SO2 + Bromine gas + water - SO2 is choking gas, would see effervescence - bromine gas is orange vapour

Does Cl- reduce H2SO4?

No, it is not a powerful enough reducing agent, only HCl is formed

How do you test for carbonate ions?

1) Add strong acid to sample 2) Collect gas produced 3) Pass trough limewater (if it turns cloudy, CO2 was produced, and there should be fizzing)

How do you test for sulfate ions?

Add dilute hydrochloric acid and barium sulfate {edit; i think this is supposed to say barium chloride} to the sample - white ppt forms

How do you test for ammonium ions

Add NaOH to the sample and warm it 2) test the gas produced with red litmus paper (should turn blue)

Describe the experimental procedure to compare the thermal stability of group 2 nitrates

Workable method could be: * first one to relight glowing splint/produce brown fumes Use the same heat (i.e. by using same flame of same bunsen burner) Use the same moles (amount) of each nitrate in separate test tubes MUST USE A FUME CUPBOARD do not use a gas syringe for measuring rate of thermal decomposition reactions because it could be air which expanded due to heat

What is the observation when nitrate ions is heated with concentrated sulfuric acid and a reducing agent?

NO2 (nitrogen dioxide gas) is evolved which is brown

Explain why hydrogen bromide, which is a colourless gas, appears as misty fumes when it makes contact with moist air.

(1) HBr dissolves in water in the air (2) and forms droplets of hydrobromic acid.