Inorganic chemistry and periodic table Flashcards
How does atomic radius change across group 2?
increases due to more shells of electrons.
How does melting point change down group 2?
melting point decreases
due to metallic bonding becoming weaker
reducing the electrostatic attraction between cations and delocalised electrons
due to the metal ions and delocalised electrons having a greater distance from each other.
How does 1st ionisation energy change across group 2?
decreases
Because atomic radius increases due to more shells
increased shielding.
so more repulsive force of inner shells.
How does reactivity of group 2 change down the group?
increases down the group.
because more shielding
more repulsive force by inner electrons
so easier to form cation.
how do group 2 metals react with oxygen?
- will burn in oxygen, with Mg forming a bright white flame
what can be used to clean off the MgO before using in an experiment?
emery paper
give the balanced symbol equation for Mg and O
2Mg + O2 —-> 2MgO
How does Mg react with chlorine? give the equation
Mg + Cl2—-> MgCl2
How does Mg react with steam?
forms MgO + H2 by reacting with steam.
How does Mg react with warm water?
Forms Mg(OH) 2 + H2 through a much slower reaction
what pH would you expect a concentrated solution of Mg(OH)2 to be?
10-14
what would be OBSERVED when group 2 metals react with water? what is the case with calcium?
- fizzing
- metal dissolves
- the solution heats up
- calcium forms a white precipitate
How does the solubility of the hydroxides change down group 2?
- increases in solubility
what happens to group 2 solids that are not soluble?
they appear as white precipitates
how to group 2 ionic oxides react with water?
form hydroxides
why are ionic oxides basic?
oxide ions accept protons to become hydroxide ions.
order these from most to least soluble:
Mg(OH)2
Ca(OH)2
Ba(OH)2
Ba(OH)2
Ca(OH)2
Mg(OH)2
give a use of Mg(OH)2
used to neutralise excess acid in the stomach to treat constipation.
Give uses for Ca(OH)2
used to neutralise acidic soils in agriculture
rate from most to least alkaline:
Mg(OH)2
Ca(OH)2
Ba(OH)2
Ba(OH)2
Ca(OH)2
Mg(OH)2
How does the solubility of sulfates change in group 2?
- decreases
Explain the reaction between Ba and sulfuric acid
will form BaSO4 and H
reaction is slow as BaSO4 that is produced is insoluble and will only act as a barrier from further reacting.
define thermal decomposition
The use of heat to break down a reactant into more than 1 product.
How to group 2 carbonates thermally decompose?
Form group 2 oxides and CO2
How does thermal stability change down group 2?
Becomes increasingly thermally stable.
Cations get bigger
have less of a polarising effect
distort the carbonate ion less
so less easily breaks down.
So stronger C-O bond
How do group 1 carbonates thermally decompose?
do not decompose except Li.
Because they only form a 1+ charge and dont have a big enough charge to polarise the carbonate ion.
Li can because it’s ionic radius is small enough to have the polarising effect.
outline an experiment that can be done to investigate the ease of decomposition.
heat known mass of carbonate in a side arm boiling tube, passing the gas through a bung and tube to limewater.
repeat with diff carbonates and same volume of limewater and same distance from bunsen burner flame.
what is produced when group 2 Nitrates decompose?
NO2
Metal oxide
Oxygen
Why do Nitrates become more stable down the group?
Nitrate ion has large electron cloud that can be distorted.
so since atomic radius increases down the group, charge is spread over a larger area
So the less distortion, the more stable it is since charge densities balance each other out.
describe the method to carry out a flame test
- use a nichrome wire
- clean the nichrome wire with HCL to prevent any contamination from other metals that may mask colours
- heat wire in bunsen burner flame
- grind up sample
- dip wire in it and test.
Give the colours of the following metals:
- Lithium
- Rubidium
- Sodium
- Caesium
- Magnesium
- Strontium
- Barium
- Potassium
- Calcium
- Scarlett red
- red
- yellow
- blue
- no colour (not in visible light spectra so will see orange flame)
- red
- apple green
- lilac
- brick red
explain the occurence of flame colours
- heat from the flame causes electrons to move to a higher energy level
- since it is instable at a higher energy level, it drops down.
- The energy emitted from this is in the form of wavelength- which if part of the visible light spectrum, can be seen.
what is the trend in melting and boiling point for halogens? Explain
- increase down the group
- Because atomic radius increases, so have more electrons
- meaning they have larger London forces between molecules, so more energy needed to break them.
What is the trend in electronegativity down the group? Why?
Decreases
Because more electrons= larger atomic radius, so nucleus and bonding pairs attraction would be lower.
What is the trend of reactivity down group 7? Why?
Decreases
Because larger atomic radius
less shielding
so attracting an electron becomes harder, so harder to form 1- ions
how does oxidising power change down group 7?
- decreases down the group
- since harder to accept an electron
- due to more electron shells.
- so less attraction between nucleus and electrons
Which ion will displace bromide and iodide.
chloride
which ion will displace only iodide ions?
Bromide
what is observed when potassium chloride and the following react together:
- Chlorine
- Bromine
- Iodine
- very pale green solution- no reaction
- yellow solution- no reaction
- Brown solution- no reaction
What is observed when Potassium bromide reacts with the halides?
Chlorine: Chlorine displaces Bromine, so yellow solution is formed.
Bromide: No reaction, yellow solution
Iodide: brown solution no solution
What is observed when Potassium iodide reacts with the halides?
Chloride: chlorine displaces, Brown solution.
Iodide: no reaction, brown
Bromide: Bromine displaces, brown solution forms.
what colours are seen on the top layer when an organic solvent is added to the halogens?
Chlorine: colourless
Bromine: yellow
Iodide: purple
What observations will be made when an organic solvent like hexane is added to the oxidation reactions of the halides?
Every reaction the same, except all iodide reactions will be purple except chlorine and iodine (potassium halides) as it displaces iodine.
define disproportion reaction
When an element is being simultaneously oxidised and reduced.
state the balanced equation for the reaction of chlorine with water.
Cl2 + H2O —> HClO + HCl
If universal indicator is added to the solution of chlorine and water, what will be observed?
- would turn red due to its acidic pH
- then would be turn colourless due to HClO bleaching the solution.
What are the reactions of halides with cold NaOH
What are the reactions of halides with warm NaOH
use Cl as an example
- NaCl
- HClO
- H20
With warm:
Same products except forms NaClO3
What is the balanced equation for NaF and H2SO4?
What are the observations?
NaF + H2SO$—> NaHSO4 + HF
white steamy fumes are produced of HF.
What is the balanced equation of NaCl and H2SO4? What is observed?
- NaCl + H2SO4 —-> HCl + NaHSO4
White steamy fumes of HCl seen.
How do you test for sulfate ions
HCl ad Barium Chloride, forms a white ppt
How to test for OH ions
- Litmus paper will turn from red to blue as it’s an alkali, but need further tests like spectroscopy to confirm they are actually present.
How to test for halide ions?
- Nitric acid, then Silver nitrate
- Cl forms white pp
- I forms a yellow ppt
- Br forms a cream ppt
Further tests- add dilute NH4- which will only redissolve Cl
Conc NH4 will redissolve Br but not I
How to test for Carbonate ions?
add HCL or any dilute acid
CO2 would be produced- test with limewater.
Should turn cloudy.
Sr, Li and Rb nitrates are all white solids. Explain how you would identify each apart from ppt reactions and decomposition reactions. No practical details are required.
- On decomposition, Li and Sr would produce a brown coloured gas
- but RbNO3 would not
- Dissolving each in distilled water, making a solution, adding NaOH
- a white ppt would be seen only for Sr2NO3
- but nothing seen for LiNO3 and RbNO3
