Everything Flashcards
Explain how geometric isomerism arises in but-2-ene.
The double bond is formed by overlap of adjacent p-orbitals
Explain why atom economy for formation of 2-bromobutane is different for each reaction.
Atom economy with but-2-ene is 100%
With but-1-ene some 1-bromobutane forms so it is less than 100%
Name the product if the reaction between but-2-ene and acidified potassium manganate.
2,3-butandiol
State a problem associated with the disposal of used polymer products.
They are not biodegradable
State one way in which the use of polymers can be made more sustainable.
Recycling
Reusing
Using renewable energy sources in their production
Using chemicals from plants
The reaction of methane and chlorine is a free radical substitution.
State the essential condition for this reaction.
Ultraviolet radiation
Explain fully what a curly half arrow represents in a free radical mechanism.
A single electron
Transferring from a bond to an atom
Explain why the amount of chloromethane formed in a propagation stage is much greater than the amount made in the termination stage.
- Free radicals are generated in propagation
- Propagation stage keeps repeating
- In termination two radicals form one product
Define standard enthalpy change of combustion.
- Energy change
- When 1 mole of substance combusts
- Completely under standard conditions
Write the chemical equation for the formation of nitric acid.
H2SO4 + NaNO3 ———> HNO3 + NaHSO4
Suggest why nitric acid needs to be stored in brown glass bottles.
To prevent it reacting in sunlight
Outline the steps required to determine the percentage of gold in an alloy of gold, silver and copper.
- Dissolve in excess nitric acid
- Filter, wash and dry
- Weigh allow at start and weigh gild at end
Write the ionic equation for the formation of magnesium nitrate and hydrogen.
Mg (s) + 2H+ (aq) ———> Mg2+ (aq) + H2(g)
Explain why cyclooctane is added to petrol.
It has higher octane rating
This gives more efficient combustion
How does the addition of a catalyst lower the temperature required for a reaction?
- Lowers activation energy
- By providing alternative pathway
- Same no. Of particles can react at lower temp
(Graphite)
Identify weak intermolecular forces and describe how they arise.
- London forces
- Instantaneous dipole due to electron distribution
- Induced dipole in adjacent layers
Suggest why a very high temperature and high pressure are needed to convert graphite to diamond.
- Equilibrium shifts right
- Reaction is more endothermic
- High pressure favours higher density
- High temp and pressure needed because activation energy is high
Explain why ionisation is an endothermic process.
To overcome electrostatic attraction of for electrons
Describe the trend in first 4 ionisation energies for aluminium.
- Gradual increase in first 3 energies
- Big jump from 3 to 4
- Group 3
Why are orbitals of the same sub shell occupied singly by electrons before paring of electrons occurs?
Electrons in the same orbital repel each other
A sulfur atom can expand its octet but an oxygen atom cannot.
Suggest why this is so.
- Sulfur has 3d orbitals that can be occupied
2. Oxygen is in Period 2 and has no available d orbitals
Deduce the shape of a sulfur dioxide molecule and suggest the bond angle.
- Bent
2. 104.5
Outline how a solid sample of element X is converted into ions in a mass spectrometer.
- Vapourised
2. Atoms bombarded with high energy electrons
Following formation of ions there are three steps in the production of a spectrum in the mass spectrometer.
Name the steps in order and state how the first 2 are carried out.
- Acceleration - ions passed through electric field
- Deflection - ions pass through magnetic field
- Detection
State what is meant by a covalent bond.
Strong electrostatic attraction between two nuclei and shared pair of electrons
What is the bond angle in BF3?
120
How is a dative covalent bond formed?
- Donation of lone pair
2. To the atom which is electron deficient
Explain why 1st ionisation energy of H2 is less than He but more than Li.
- He more protons than H
- He outer electron in same shell as H
- Li outer electron in higher energy level
- Shielded by inner electrons
Hydrogen can be placed in several different positions in periodic tables.
Criticise the position of hydrogen immediately above lithium.
- H has 1 electron in s orbital
- Rest of group 1 are alkali metals
- Hydrogen doesn’t react in same way
Addition of barium chloride to one of the test tubes gave a white precipitate.
Identify two possible anions.
SO4 (2-)
CO3 (2-)
Explain why iodine and chlorine have many similar chemical reactions.
- 7 electrons in outer shell
2. Number of electrons in outer shell determine chemical reactions
What are the oxidation numbers for:
S2O3 (2-)
SO4 (2-)
S4O6 (2-)
- 2+
- 6+
- 2.5+
Write the ionic half equation for the reaction of aqueous S2O3 (2-) to give SO4 (2-).
S2O3 (2-) + 5H2O ——> 2SO4 (2-) + 10H+ + 8E-
Explain why the ions in sodium fluoride are described as isoelectronic.
Same electronic configuration
Explain how changes in the cation affect bond strength in an ionic compound.
- Higher the charge on cation the stronger the attraction between ions
- Smaller the radius of cation the stronger the attraction between ions
- Li+ is smaller than K+
Explain why diamond and sodium chloride have high melting points.
- Diamond - strong attractive forces between C atoms need to be broken
- NaCl - strong electrostatic attractive forces between oppositely charged ions need to be broken.
What is meant by the term s-block element?
- Elements with electron arrangement
- Differs from previous element
- Having 1 more electron in S orbital
Compare 1st IE of nitrogen and oxygen.
- N - 2p electron being lost is unpaired but for O it is paired
- 2 electrons in same orbital repel
- Easier to remove
- IE of N is higher
Why does 1st IE increase across a period?
- Nuclear charge increases
- Greater attraction between nucleus and electrons
- Electrons pulled towards nucleus decreasing atomic radius
Why is 1st IE of aluminium less than Mg?
- 3p electron more distant from nucleus than 3s
- Partially screened by 3s2 electrons
- As well as inner electrons
Define relative isotopic mass.
- Mass of an atom of an isotope
- Compared with 1/12 of mass of an atom
- Of carbon 12
Define relative molecular mass.
- Weighted average mass of a molecule
- Of an element or compound
- Compared to 1/12 of the mass of an atom
- Of carbon 12
Describe 2 differences in orbital overlap of sigma and pi bonds.
- Sigma - single area of overlap and axial overlap
2. Pi - two areas of overlap and parallel overlap
