Chemistry Model Answers Flashcards
Hydroxide and acid makes…
Salt
Water
BF5⃣
5 bond pairs
BRE
Trigonometry bipyramidal
120 or 90
Ammonia and acid makes…
Ammonium salt NH4⃣
Acid and alkali makes?
Salt
Water
Acid and metal carbonate makes…
Salt
Water
Carbon dioxide
Oxide and acid makes
Salt
Water
Ionisation energy down a group
Decreases because ... NC increases but outweighed shielding AR increase NA decrease Shielding increase Easier to remove outmost electron
Common acids
HCl
H2⃣SO4⃣
HNO3⃣
Hydrocarbonates and acid makes..
Salt
Water
Carbon dioxide
Writing ionic equation
Only separate aqueous solutions
Observations
Dissolving of metals, metal carbonates or soluble bases when reacted with acid
Effervescence is gas is produced
Common bases
Metal oxides
Metal hydroxides
Ammonia
Properties of giant metallic lattices
High melting points Strong due to attractions between ions and delocalised electrons Malleable Ductile Not brittle They conduct - delocalised electrons
NH3⃣
3 bond pairs 1 lone pair LPRMTBP Pyramidal 107
Command alkalise
Sodium hydroxides
Potassium hydroxide
Aqueous ammonia
Ionisation energy across a period…
Increases because... NC increase AR decrease NA increase Shielding insignificant
Why is helium the highest first ionisation energy?
Electrons occupy the first shell
Electrons are very close to the nucleus
No other electrons so no shielding
More protons than hydrogen so stronger nuclear charge so electrons are held more strongly
Van der waal going down the group
More electrons
More van der waals
More energy needed to break them
Drawing an ionic bond
Anions have a mixture of its own and transferred electrons
Cations have no electrons shown
Relevant charges on the outside of the squared brackets
What does an acid and metal make?
Salt
Hydrogen
Giant ionic lattice properties and explanations
High melting and boiling point - held together by string ionic bonds in the lattice so a lot of energy is needed to break the bonds
Very brittle - if the layers slide over each other, the charges with repel each other
Do not conduct when solid - ions are held strongly in lattice
Conduct when molten or aqueous - ions are mobile
Insoluble in non polar solvents - soluble in water because it is polar
BeCl2⃣
Describe bonding and structure
2 bond pairs
Bonds pair repel equally
Linear
Bind angle is 180
Giant covalent lattice examples
Diamond
Graphite
Silicon
Silicon dioxide
CH 4⃣
Bonding and structure
4 bond pairs
BRE
Tetrahedral
109.5
SF6⃣
6 bond pairs
BRE
Octahedral
90
How are van der waal formed?
Uneven distribution if electrons
Increase temporary dipole
Induces dipole on neighbouring molecules
H2⃣O
2 bond pair 1 lone pair LPRMTBP Angular or bent shape 104.5
Simple molecular ( covalent ) structures
Any other covalent compound like H2⃣O, CH4⃣, Cl2⃣, CiCl4⃣
All have intermolecular forces
Requirements for coordinate bonding
Lone pair of electrons
Space to accept pair of electrons
What different about graphite to the other giant covalent lattice molecules?
Intermolecular forces and some different properties
Comparison between properties of graphite and the other covalent structures
Diamond, silicon and silicon dioxide
High melting points due to strong covalent bonds therefore large amount of energy required
Hard as they exist in a rigid tetrahedral structure with coordination number if 4
Does not conduct because there are no mobile electrons as the carbon use all four atoms for bonding
Graphite
High melting points due to strong covalent bonds therefore large amount of energy required
Soft because it consists of layers attracted by weak van der waal forces and layers slide over each other
Conducts electricity because each atom only uses 3 of its outer shell electrons for bonding ( coordination number of 3) and remaining delocalised electrons can move through layers allowing conductivity
H—-Cl
Polar or non polar?
Explain
Polar
Non symmetrical
Dipole do not cancel
Permanent dipole
Explain why S8⃣ has a higher melting point the Cl2⃣
S had stronger van der waal forces than Cl
S has more electrons in its structure
CCl4⃣
Polar or non polar?
Explain
Non polar
Symmetrical
Dipoles cancel
Van der waals
BF3⃣
Bonding and structure?
3 bind pairs
BRE
Trigonal planar
120
Unusual facts about water
Ice - simple molecular lattice, volume larger than the water making it, ice floats due to hydrogen bonds being further apart
Water has higher than expected boiling point - hydrogen bond is strongest intermolecular force
Water expands when frozen therefore ice is less dense - hydrogen bonds are longer than covalent so takes up greater volume
High surface tension due to extra attraction between molecule just below the surface
High viscosity of water
H2⃣O
Polar or non polar?
Explain
Polar
Non symmetrical
Dipoles do not cancel
Permanent dipole
Explain why the electrical conductivity increases from Na to Al
Number of delocalised electrons in metallic lattice increase
Explain why the elements P to Ar cannot conduct electricity
They contain no delocalised electrons or mobile ions
Group two reactions with water
Mg + 2H2⃣O —> Mg(OH)2⃣ + H2⃣
Works for any metal down group 2
Mg + 2H2⃣O –(steam)–> MgO + H2⃣
Only magnesium
Mg(OH)2⃣ pH 8. Used in antacids or toothpaste. |
Ca(OH)2⃣ pH 10. Used to neutralise acidic soil. |
Sr(OH)2⃣ pH 12. |
Ba(OH)2⃣ pH 14. |
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Hydroxide more soluble down a group
Group two metals react more vigorously with cold water
Explain why the melting and boiling point increase from Na to Al
Strength of metallic bond increases
Number of delocalised electrons added to metal structure increases
Al has a greater charge of +3
Therefore more energy is needed to break the bonds
Explain why silicon has such a high melting point
Silicon has a giant covalent structure
Contain many string covalent bonds
Large amount of heat energy needed to break the bonds
Melting points down group two elements
Decreases Nuclear attraction decrease Nuclear charge increases but outweighed by shielding Shielding increases Easier to remove outermost electron Weaker metallic bonds Ionic radii increase
Reaction with oxygen - group two
Group two metals react more vigorously down the group when reacted with group 2
Properties of intermolecular forces
Low boiling point due to weak intermolecular van der waal forces so little energy is needed
As a result they tend to gases or liquid at room temperature
Iodine is an exception
Do not conduct electricity due to not mobile electrons
More soluble in organic solvents than water due to van der waal forces between molecular structure and solvent molecule
What colour is bromine at rtp and state?
Red brown liquid
Group 2 reaction with oxides
More soluble down the group
Down the group gets more basic
No redox reactions
Group 2 carbonates
Thermal decomposition increases down the group
No effervescence
Down group carbonates are more difficult to decompose
What colour is fluorine at rtp and state?
Yellow gas
Boiling point down group 7
Increases
More electrons
More van der waals
More energy needed to break bonds
What colour is chlorine at rtp and state?
Green gas
What colour is iodine at rtp and state?
Grey solid
Electro negativity down group 7
Decreases Nc increases outweighed by shielding NA decrease AR increase Shielding increase
Ionic equation when mixing silver nitrate
Ag+ (aq) + Cl- (aq) —-> AgCl (s)
Reactivity down group 7
Decreases AR increase Shielding increase NC increase is outweighed NA decrease Elements find harder to gain electrons
Are halogens good oxidising agents?
Yes
What is the reactivity down group two
Increases Atomic radii increase Shielding increase Nuclear charge increase but outweighed by shielding Nuclear attraction decrease Outer electron lost more easily
Colours of halogens in organic solvents like cyclohexane
A) chlorine
B) bromine
C) iodine
A) pale green
B) orange
C) purple/lilac
Chlorine with water symbol and word equation
What sort of reaction is this?
Cl2⃣ (g) + H2⃣O (l) –> HCl (aq) + HClO (aq)
Chlorine plus water gives hydrochloric acid plus chloric (I) acid.
Disproportionation reaction
In the reaction with chlorine and water, why is chlorine used?
What is wrong with using chlorine?
Chlorate ion kills bacteria
Chlorine is toxic
What does chlorine and cold, aqueous sodium hydroxide make?
Bleach
Solubility of halides in dilute ammonia solution
A) chloride
B) bromide
C) iodide
A) soluble
B) insoluble
C) insoluble
Colours of Halogens in aqueous solution :
A) chlorine
B) bromine
C) iodine
A) pale green
B) orange
C) brown
Solubility of halides in concentrated ammonia solution
A) chloride
B) bromide
C) iodide
A) soluble
B) soluble
C) insoluble
Test for halides
Add aqueous silver nitrate and if white precipitate forms chloride present
If cream precipitate forms bromide is present
If yellow precipitate forms iodide is present
