Group 2 Alkaline Earth Metals And Redox Flashcards
Describe the trends in atomic radius down group 2
It increases as extra electron shells are added as u go down the group
Why does first ionisation energy decrease down group 2
The outer electron is in a higher energy level and there’s an increase in shielding .
Outer electrons are further from the nucleus reducing the nucleus attraction
How does reactivity increase down group 2
Reactivity increases down group 2 because it’s easier to lose electrons
Why does melting point decrease
Why’s there a dip at mg
as the metal ions get larger the distance between the bonding electrons (outer e-) and the positive nucleus gets larger and reduces the overall attraction between the two.
The crystal changes
As you react group 2 elements with hydroxides down the group..
Sulfate
It goes from least to most soluble
Most to least
Test for identifying sulfate ions in solution
Add dilute hcl and then barium chloride solution to a solution containing sukfate ions a white precipitatie forms (barium sulfate ) bc barium is insoluble
Use of barium metal
I, used in barium meals to diagnose stomach problems.
Barium sulfate is insoluble so jt forms a suspension rather than a solution
Mg is used as…
Part of the process of extracting titanium from its ore
Removal of sulfur dioxide from flue gases
It can be removed from flue gases by reacting with an alkali
Describe the trends in boiling points of group 7 down the group
Increases, as vanderwalls forces increase in strength as size of molecule increases
Describe the trends in electronegativity of group 7 elements down the group
Decreases down the group , outer electrons r getting further from the nucleus as they are more shielded
Why does group 7 get less reactive down the group
Atoms become larger and the outer shell is further from nucleus
What happens when u add chlorine to a solution containing bromide ions ?
Chlorine displaces the bromide ions . Colourless to orange
What happens when u add chlorine to potassium iodide ions
Chlorine displaces the iodide ions . Colour change from colourless to brown
If u add bromine to a solution of potassium iodide
Bromine displaces the iodide ions , colourless to brown
The reducing power of halides..
Increase down the group as it’s easier to loose the outer electron because the electrons are held less strongly by nucleus
Test for halide ions
How to test further
Add nitric acid to remove any ions interfering w experiment , add silver nitrate solution , chloride = white pptp. Bromide = cream pptp . Iodide = yellow ptp
Add ammonia. Silver chloride pptp dissolves in dilute NH3 . Silver bromide ptp dissolves in conc NH3
.silver iodide ptp is insoluble in conc NH3
describe how to carry out a flame test:
test for froup 2 ions
1 dip wired loop into conc hcl to clean, dip into unknown compound, hold loop in blue part of bunsen flame
calcium ion = brick red.
strontium = red
barium = pale green
how to identify group 2 ions using NaOH
add naoh to test tube containing solution and observe ptp then keep adding excess naoh
mg = slight white pptp excess = white pptp
calcium = slight white pptp
strontium = slight white pptp
barium = no change
test for ammonium ions
hold damp red litmus paper over substance being tested , damp paper will turn blue if there are ammonium ions
another method - add NaOH solution to solution being tested , heat , damp red litmus paper turns blue due to ammonia gas given off
how to test for carbonate ions?
add dilute HCL, if solution containing carb ions will fizz this is C02 gas
to test this c02 further bubble it thru limwater, itll turn cloudy. confirming there is carb ions
The use of Mg(OH)2
Ca(OH)2 in
group 2
medicine
agriculture.
the reaction between chlorine gas and cold NaOH solution
produces sodium chlorate (NaCLO) solution
-this is bleach which kills bacteria , used in water treatment
-in this reaction chlorine is ox and red which is disproportionation
chlorine gas and water makes
chloride and chlorate ions
uses of chlorine
kills bacteria
its toxic and harmful if breathed in. its still used tho because the cancer risk is small compared to the risks of drinking untreated water
Conditions for the electophillic substitution reaction between hydrogen halides and alkenes
Ethene gas is passed thru conc HBR
How are alkenes identified ?
If an alkene is present the bromine water solution turns from orange to colourless
What is an electrophile and give 3 examples
- an electron acceptor attracted to areas of high electron density (the double bond )
- HBr, Br2 and H2S04
Conditions for h2so4 electrophillic addition
Ethene gas is passed thru cold conc h2so4
hydration of ethene adv and disadv
A Forms pure product, better atom economy
D- uses lots of energy and fossil fue,s , non renewable,
Fermentation of glucose adv and disasv
a - uses less energy , lower equipment cost
D - slower reaction , land for crops needed
Properties of polymers
- saturated, main carbon chain is non polar so t makes them unreactivw
- How are addition polymers produced ?
From alkenes where the double bond is broken to form a repeating unit
- how can reaction conditions affect the polymers produced ?
High pressures and temps produce branched chain polymers with weak im forces . Lower temps and pressures produces straight chain polymers with strong im forces
- what is PVC?
An addition polymer with water proof properties , it gains these properties by the addition of plasticisers during the reaction
