module 3 Flashcards
A student bubbles chlorine gas through aqueous potassium iodide. A reaction takes place.
State what the student would observe.
(The solution would turn) yellow OR orange OR brown
Chlorine gas can be added to a cold, dilute alkaline solution to form bleach. Write the equation for this reaction.
Write the ionic equation for this reaction
.Include state symbols.
Cl2 + 2NaOH NaClO + NaCl + H2O
Cl2 (g) + 2I– (aq) I2 (aq) + 2Cl– (aq)
State whether the following substances conduct electricity when solid or molten, and explain your answers in terms of the particles involved:
• aluminium
• aluminium fluoride
• boron tribromide.
Conductivity of Al mark
M1: Aluminium conducts in solid and molten states
Reason for conductivity of Al mark
M2: Aluminium has delocalised electrons
Conductivity and reason for molten AlF3 mark
M3: Aluminium fluoride conducts when molten
AND
because it has mobile ions
Conductivity and reason for solid AlF3 mark
M4: Aluminium fluoride does not conduct when solid
AND
Solid aluminium fluoride has ions which are fixed (in
position) OR ions are held (in position) OR ions are not
mobile
AND
In an (ionic) lattice OR (ionic) structure OR by (ionic)
bonds
A student prepared some calcium hydroxide by adding a small piece of calcium to a large excess of water.
Describe what the student would observe and write the equation for the reaction.
Effervescence OR fizzing OR bubbling OR gas produced
AND
The solid OR calcium OR the metal would dissolve OR
disappear OR a (colourless) solution forms
Ca + 2H2O Ca(OH)2 + H2
State how and explain why the attraction between nuclei and outermost electrons in gaseous atoms varies across Period 3.
The attraction (between nuclei and outermost electrons) increases (across the period) AND The nuclear charge increases OR The number of protons increase (Outer) electrons are in the same shell OR (Outer) electrons experience similar shielding OR Same number of shells OR Atomic radius decreases
The table shows the boiling points of ammonia, fluorine and bromine.
Boiling point / °C
ammonia, NH3 – 33
fluorine, F2– 188
bromine, Br2 59
Explain the different boiling points of NH3, F2 and Br2. Include the names of any relevant forces and particles.
M1 NH3 forces mark
NH3 has hydrogen bonding
M2 F2 AND Br2 forces mark
F2 AND Br2 have van der Waals’ (forces)
M3 Type of particle mark
Forces OR attractions are between molecules OR are
intermolecular for ammonia
AND
Forces OR attractions are between molecules OR are
intermolecular for fluorine OR for bromine
Silicon dioxide, SiO2, has the same structure and bonding as diamond.
State the structure and bonding in SiO2.
Giant covalent (lattice)
Describe and explain the electrical conductivity of sodium oxide, Na2O, and sodium in their solid and molten states.
Conductivity of Na mark
M1: Sodium conducts in the solid and molten states
Reason for conductivity of Na mark
M2: Sodium has delocalised electrons (in both solid and
liquid state)
Conductivity of Na2O mark
M3: Na2O conducts when molten and not when solid
Reason for conductivity of Na2O marks
M4: Molten Na2O has ions which are mobile
M5: Solid Na2O has ions which are fixed (in position) OR
ions are held (in position) OR ions are not mobile
AND
in an (ionic) lattice OR structure
Elements in the Periodic Table show a periodic trend in atomic radius.
State and explain the trend in atomic radius from Li to F.
M1 Trend AND nuclear charge mark (from Li to F) atomic radius decreases AND nuclear charge increases or number of protons increases M2 same shell/shielding mark (outer) electrons are in same shell OR (outer) electrons experience similar or same shielding OR same number of shells M3 nuclear attraction mark Greater nuclear attraction on (outer) electrons or shells OR (Outer) electrons or shells are attracted more strongly to the nucleus
A student adds a small volume of aqueous silver nitrate to an aqueous solution of bromide ions in a test-tube. The student then adds a similar volume of dilute aqueous ammonia to the same test-tube.Describe what the student would see in the test-tube after the addition of aqueous ammonia.
Write an ionic equation for any precipitation reaction which occurs in the student’s tests.Include state symbols.
Cream AND precipitate
Ag+(aq) + Br–(aq) AgBr(s)
Chlorine reacts with aqueous sodium hydroxide to form bleach.Write the equation and state the conditions for this reaction.
Equation
2NaOH + Cl2 NaCl + NaClO + H2O
Conditions
cold AND dilute (sodium hydroxide)
Under different conditions, chlorine reacts differently with aqueous sodium hydroxide.
A disproportionation reaction takes place as shown below.
3Cl2(g) + 6NaOH(aq) 5NaCl (aq) + NaCl O3(aq) + 3H2O
State what is meant by disproportionation and show that disproportionation has taken place in this reaction.
Use oxidation numbers in your answer.
Definition of disproportionation mark
M1 (Disproportionation) is the (simultaneous) oxidation
and reduction of the same element (in the same redox
reaction)
M2 Assigning of oxidation numbers
Cl in Cl2 is 0 AND Cl in NaCl is -1 AND Cl in NaClO3 is +5
M3
Chlorine has been oxidised from 0 to +5
AND
Chlorine has been reduced from 0 to –1
‘Chlorine has been oxidised from 0 in Cl2 to +5 in NaClO3
and chlorine has been reduced from 0 in Cl2 to -1 in NaCl’
would secure M2 and M3
3Cl2 + 6NaOH 5NaCl + NaClO3 + 3H2O
0 -1 +5
reduction
oxidation
This diagram, along with a correct definition, would secure
all three marks.
Write the equation for the thermal decomposition of calcium carbonate.
Include state symbols.
CaCO3(s) CaO(s) + CO2(g)
Write the formula of the Group 2 carbonate which decomposes at the highest temperature.
BaCO3 OR RaCO3
A student tests chlorine gas with damp blue litmus paper. The litmus paper first turns a red colour and is then bleached. A reaction takes place between chlorine and water in the damp litmus paper.
Write the equation for the reaction between chlorine and water.
Explain why the damp litmus paper turns a red colour as a result of this reaction.
Cl2 + H2O HCl + HClO
H+ ions are released OR HCl is acidic OR HClO is acidic
Bleach is made by reacting chlorine with cold dilute aqueous sodium hydroxide.
Suggest the formula of the ion responsible for bleaching.
ClO–
Describe and explain the trend in reactivity of Group 2 elements with chlorine as the group is descended.
Reactivity increases (down the group) Increasing size mark Atomic radius increases OR There are more shells Increased shielding mark There is more shielding Nuclear attraction (to electron) mark Nuclear attraction (to electron) decreases OR (outermost) electrons experience less attraction (to nucleus) OR Increased nuclear charge is outweighed by increased shielding/distance Ease of electron loss mark Easier to remove (outer) electron(s) OR Ionisation energy decreases
State the reagent that the student would need to add to the solution of calcium iodide.
AgNO3(aq) OR silver nitrate OR AgNO3
What observation would show that the solution contained iodide ions?
Yellow AND precipitate
Write an ionic equation, including state symbols, for the reaction that took place.
Ag+ (aq) + I–
(aq) AgI(s)
The student is provided with an aqueous solution of calcium bromide that is contaminated with calcium iodide.The student carries out the same chemical test but this time needs to add a second reagent to show that iodide ions are present.State the second reagent that the student would need to add.
concentrated (aqueous) NH3
Explain the trend across Period 2 shown
Nuclear charge mark
(Across the period) number of protons increases
OR
greater nuclear charge
Quality of written communication – nuclear OR
proton(s) OR nucleus spelled correctly ONCE for the first
marking point
Distance / shielding mark
(Outermost) electrons are in the same shell
OR
(Outermost) electrons experience the same shielding
OR
Atomic radius decreases
Nuclear attraction (to electron) mark
Greater nuclear attraction (on outermost electrons)
OR
(outer) electrons are attracted more strongly (to the
nucleus)
Explain why it is unnecessary to refer to carbon as either diamond or graphite
(Diamond and graphite form) gaseous atoms (of carbon
when they are ionised)
What is the name of the term used to describe the repeating patterns in the Periodic Table?
periodicity
Melting points show a trend across a period.The table below shows the melting points of three elements in Period 3 of the Periodic Table.
element aluminium silicon phosphorus
melting point 660 1410 44
Explain the trend shown in terms of bonding and structure.
Al bonding mark
Al has metallic (bonding) OR has (electrostatic) attraction
between positive ions and (delocalised) electrons
Si bonding mark
Si has covalent (bonding) OR has shared pairs of
electrons between atoms
P bonding mark
P has induced dipoles OR has van der Waals’ forces
(between molecules)
Structure mark 1
Al AND Si are Giant
Structure mark 2
P is Simple molecular OR simple covalent
Bond strength mark
Metallic AND covalent are stronger than vdWs
OR
Bonds broken in Al AND in Si are stronger than the forces
broken in P
OR
More energy is needed to overcome bonds in Al AND Si
than the forces in P
Write an equation to represent the second ionisation energy of magnesium. Include state symbols.
Mg+(g) Mg2+(g) + e–
Equation correct
State symbols correct
Magnesium has a greater second ionisation energy than strontium.
Explain why.
Ionic radius mark
Mg(+) has smaller (ionic) radius OR has less shells
Shielding mark
(outermost electron) of Mg(+) experience less shielding
Nuclear attraction mark
More nuclear attraction on (outermost electrons)
OR
Outer electrons are attracted more strongly (to the
nucleus)
Suggest two compounds which could be reacted together to produce Sr(OH)2.
SrO AND H2O
Write an equation to show how HClO can form in drinking water.
Cl2 + H2O HClO + HCl
Some scientists believe that chlorine compounds should not be present in drinking water.
Suggest one reason why scientists may be worried by the presence of these compounds.
(Chlorine compounds are) carcinogenic
OR
(Chlorine compounds are) toxic OR poisonous
Chlorine reacts directly with Group 2 elements to form chlorides that are very soluble in water.Aqueous chloride ions can be detected by adding aqueous silver nitrate.
The appearance of solid silver chloride, AgCl, confirms the presence of chloride ions.
State the type of reaction that has taken place.
Write the ionic equation for this reaction. Include state symbols.
Precipitation
Ag+(aq) + Cl–(aq) AgCl(s)
When chlorine gas is bubbled through aqueous potassium iodide, a reaction takes place.
Write the ionic equation for this reaction.
Cl2 + 2I– 2Cl– + I2
Describe a chemical test which the student could have carried out to prove that the filtrate contains aqueous chloride ions.
Add (aqueous) silver nitrate OR AgNO3 OR Ag+ ions
white AND precipitate
The student decided to prepare barium bromide, BaBr2, by directly reacting barium with bromine gas.The student was unsure whether this preparation would be more reactive or less reactive than the preparation of CaCl 2 in
Explain why the student was unsure of the relative reactivity of the two preparations.
Ba is more reactive than Ca ORA
Br2 is less reactive than Cl2 ORA
Define the term first ionisation energy.
Energy (needed) to remove an electron
from each atom in one mole
of gaseous atoms
Explain why there is an increase in first ionisation energy between F and Ne.
From F to Ne
Nuclear charge mark:
Ne has (one) more proton
OR
Nuclear charge increases
Same shell or energy level mark:
(Outermost) electrons are in the same shell OR energy
level
OR
(Outermost) electrons experience the same shielding
Nuclear attraction mark:
Greater nuclear attraction (on outermost electrons)
OR
Outer electrons are attracted more strongly (to the
nucleus)
Explain why there is a decrease in first ionisation energy between Ne and Na.
From Ne to Na
Extra shell or energy level mark:
Na has (one) more shell(s) OR energy level
Shielding mark:
(Outermost) electron experiences greater shielding
Nuclear attraction mark:
Less nuclear attraction (on outermost electrons)
OR
Outer electrons are attracted less strongly (to nucleus)
What is the name for NaCl O?
sodium chlorate(I)
Explain what is meant by the term periodicity.
A repeating pattern (of properties shown across different
periods)
Bleach can be made by reacting chlorine with cold aqueous sodium hydroxide. A solution of bleach contains the chlorate compound NaClO.
Write the equation for the reaction taking place.
2NaOH + Cl2 NaClO + NaCl + H2O
Give the systematic name for NaClO3.
Sodium chlorate(V)
State one valid reason that supports the scientists’ case and state one reason why chlorine should be added to drinking water.
Chlorinated hydrocarbons are carcinogens OR toxic
OR Chlorine is toxic OR poisonous
(Chlorine) kills bacteria OR ‘kills germs’
‘kills micro-organisms’ OR ‘makes water safe to drink’
OR ‘sterilises water’ OR ‘disinfects’
A sample of brine is a concentrated aqueous solution of sodium chloride, NaCl(aq).
Describe a simple chemical test that you could carry out to show that brine contains aqueous chloride ions. How would you confirm that no other halide ions are present?
Include an ionic equation in your answer.
Add AgNO3(aq) OR Ag+(aq) OR silver nitrate OR
AgNO3
White precipitate
Ag+ + Cl– AgCl
Add dilute NH3 and precipitate (completely) dissolves
OR disappears
Group 2 elements also react with dilute hydrochloric acid.
Describe and explain the trend in reactivity of the Group 2 elements with dilute hydrochloric acid as the group is descended.
reactivity increases (down the group) Increasing size mark atomic radii increases OR there are more shells Increased shielding mark there is more shielding Nuclear attraction mark The nuclear attraction decreases OR (outermost) electrons experience less attraction (to nucleus) OR Increased shielding / distance outweighs the increased nuclear charge easier to remove (outer) electrons OR ionisation energy decreases
Why is the first ionisation energy of strontium larger than the first ionisation energy of rubidium?
Sr has one more proton
OR greater nuclear charge
(Outermost) electrons are in the same shell
OR (outermost) electrons experience same shielding
OR Atomic radius of Sr is smaller
Sr has greater nuclear attraction (on outer electrons /
outer shell/s)
OR the (outer) electrons are attracted more strongly (to
the nucleus)
Why is the second ionisation energy of rubidium larger than the second ionisation energy of strontium?
2nd IE of Rb involves removing electron from shell
closer to nucleus
Stronger nuclear attraction on (outermost electron) of Rb
OR (outermost electron) of Rb experiences less
shielding
State one use of calcium hydroxide in agriculture and suggest why the amount of calcium hydroxide used should not be excessive.
Used to neutralise acidic soils
Excess will result in soils becoming too alkaline (to
sustain crop growth)
Suggest one other difference the student would observe between the reactions of water with calcium and of water with barium.
Idea of Ba having a quicker rate OR more vigorous
reaction
State and explain the trend in the boiling points of chlorine, bromine and iodine.
boiling points increase down the group greater number of electrons OR stronger intermolecular forces OR stronger van der Waals’ forces more energy needed to break intermolecular OR van der Waals’ forces
The halogen astatine does not exist in large enough quantities to observe any of its reactions.
Why would astatine be expected to react similarly to other halogens?
Same number of outer(most) electrons OR same
outer(most) electron structure
The student added bromine water to aqueous solutions of sodium chloride and sodium iodide in separate test-tubes. The student then added an organic solvent, cyclohexane, to each test-tube and these were shaken. • State what colour you would see in the cyclohexane in each test-tube after shaking.
• Write ionic equations for any chemical reactions that take place.
• State and explain the trend in reactivity shown by these observations.
Colours:
(Add Br2 to NaCl,) (Cyclohexane layer) turns
orange OR yellow
(Add Br2 to NaI,) (Cyclohexane layer) turns purple
OR lilac OR violet OR pink OR mauve
Equation:
Br2 + 2I– I2 + 2Br–
Reactivity:
Reactivity decreases down the group
OR Oxidising power decreases down the group
Explanations:
Chlorine will gain electron easiest
OR form negative ion easiest
Because chlorine (atom) is smallest
OR Outer(most) shell of chlorine least shielded
OR Nuclear attraction on electrons of chlorine is
greatest
Suggest why the student carried out the reactions in a well ventilated area.
Bromine is toxic
Write the equation that represents the third ionisation energy of Al. Include state symbols.
Al2+(g) Al3+(g) + e–
Suggest one further displacement reaction which could be carried out to confirm the order of reactivity of Cl 2, Br2 and I2.
Addition of Br2(aq) to I–(aq) ions
State one benefit for public health, of the reaction between chlorine gas and water.
Kills bacteria OR ‘kills germs’
kills micro-organisms OR makes water safe to
drink OR sterilises water OR ‘disinfects’
The student repeated the experiment a further three times, using the same number of moles of CaCO3, SrCO3 and BaCO3. What trend in the behaviour of the Group 2 carbonates would be observed by the student?
The ease of (thermal) decomposition decreases
(down the group)
ora
Lithium has a giant metallic structure and a boiling point of 1342 °C. Describe, with the aid of a labelled diagram, the structure and bonding in lithium and explain why lithium has a high boiling point.
Diagram showing a regular arrangement of labelled
‘Li+’ or ‘+ ions’ with some attempt to show electrons
Scattering of labelled electrons between other
species
OR
a statement anywhere of delocalised electrons (can
be in text or in diagram)
The attraction between + ions and e– is strong
OR metallic bonding is strong
Explain why fluorine has a low boiling point.
F2 has induced dipoles OR temporary dipoles OR
van der Waals’ forces (between the molecules)
which are weak
Explain why lithium fluoride conducts electricity when molten but not when solid.
ons cannot move in a solid
Ions can move OR are mobile when molten
Describe and explain the trend in atomic radii of the elements Li to F across Period 2 of the Periodic Table.
(As you go across the period) The atomic radii decreases The nuclear charge increases OR protons increase electrons are added to the same shell OR shielding remains the same greater (nuclear) attraction on (outer) electrons / (outer) shell(s)
Explain why xenon has alower first ionisation energy than neon.
Xe has a bigger atomic radius OR Xe has more
shells
Xe has more shielding
The nuclear attraction decreases
OR Outermost electrons of Xe experience less
attraction (to nucleus)
OR Increased shielding / distance outweighs the
increased nuclear charge
ORA throughout
Chlorine is used in water treatment. State one advantage and one disadvantage of using chlorine in water treatment.
Advantage
removes or kills bacteria OR kills germs OR
kills micro-organisms OR make it safe to drink OR
sterilises water OR disinfects water
Disadvantage
it is toxic OR poisonous OR could form chlorinated
hydrocarbons
Write equations for these two reactions of chlorine with sodium hydroxide:
equation for reaction with dilute sodium hydroxide,
Cl2 + 2NaOH →NaClO + NaCl + H2O 3Cl2 + 6NaOH → NaClO3 + 5NaCl + 3H2O Cl2 and NaOH as reactants AND NaClO3 and NaCl as products Rest of the equation
uggest the formula of sodium chlorate(VII).
NaClO4
State which two elements from the first twenty elements of the modern Periodic Table are not arranged in order of increasing atomic mass.
Potassium AND argon
Why does the modern Periodic Table not arrange some elements, such as those in a(i), in order of increasing atomic mass?
They are arranged in increasing atomic number
OR
Neither would show properties OR trends of rest of
group
OR
Neither would show properties OR trends of rest of
period
OR
They are arranged by electron configuration
When reacted with oxygen, magnesium forms a white powder called magnesium oxide.Write the equation for the reaction of magnesium with oxygen.
2Mg + O2 → 2MgO
Strontium reacts in a similar way to magnesium. Describe one difference you might observe if strontium, instead of magnesium, was reacted with dilute hydrochloric acid.
Quicker OR more vigorous OR gets hotter
The third period of the Periodic Table features the elements magnesium and chlorine. The table below shows the melting points of these elements. element
melting point/ °C
magnesium 650
chlorine –101
Describe the structure and bonding shown by these elements. Use your answer to explain the difference in melting points.
Mg has a giant structure
Mg has metallic bonding OR description of metallic
bonding as positive ions and delocalised electrons
(There is electrostatic attraction between) positive
ions and electrons
Cl has a simple molecular OR simple covalent
(lattice)
Cl has van der Waals’ forces (between molecules)
OR
Cl has instantaneous dipole–induced dipoles
OR
temporary dipole–temporary dipole
Sodium, Na, is a metallic element.Explain, with the aid of a labelled diagram, what is meant by the term metallic bonding.
regular arrangement of labelled + ions with some attempt
to show electrons
scattering of labelled electrons between other species
OR
a statement anywhere of delocalised electrons (can be in
text below)
metallic bond as (electrostatic) attraction between the
electrons and the positive ions
Write the equation for the reaction of sodium with oxygen to form sodium oxide.
4 Na + O2 2 Na2O
OR 2 Na + ½ O2 Na2O
Explain why the first ionisation energies show a general increase from Li to Ne.
outer electrons closer to nucleus OR radii decreases
nuclear charge increases
OR protons increase
electrons added to the same shell
OR
screening OR shielding remains the same
Explain the difference between the first ionisation energies of Li and Na
atomic radii increase OR
there are more shells
there is more shielding OR more screening
Suggest why the second ionisation energy of oxygen has a greater value than the first ionisation energy of oxygen.
the O+ ion, is smaller than the O atom
OR
the electron repulsion/shielding is smaller
OR
the proton : electron ratio in the 2+ ion is greater than in
the 1+ ion
The boiling points of some Group 7 elements are shown below.
Group 7 element
boiling point / °C
chlorine –35
bromine 59
iodine 184
Explain why the halogens show this trend in boiling points.
van der Waals’ forces OR induced dipole interactions
number of electrons increases
Down the group, intermolecular forces / van der Waals’
forces increase
OR
Down the group, more energy needed to break
intermolecular / van der Waals’ forces
The table below lists some properties of graphite.
electrical conductivity good conductor
hardness soft
melting point very high
• Describe the bonding and structure in graphite.
• Explain, in terms of bonding and structure, the properties of graphite shown above.
giant covalent (lattice) 9
layers 9
Each of the three properties below must be linked to
explanation
good conductor - because it has mobile electrons OR
delocalised electrons OR electrons can move 9
high melting / boiling point - because strong OR covalent
bonds have to be broken 9
soft - because there are van der Waals’ forces OR
intermolecular forces OR weak bonds OR weak forces
between the layers
OR
soft - because layers can slide 9
Explain the difference in melting point for the elements Na and Mg.
Magnesium ions have a greater charge9
Magnesium has more
(delocalised OR outer) electrons9
Magnesium has greater attraction between ions and
electrons OR has stronger metallic bonds 9
Sulfur exists as S8 molecules and chlorine as Cl 2 molecules. Use this information to explain the difference in their melting points.
Cl2 OR S8 has intermolecular OR van der Waals’ forces
9
S8 has stronger intermolecular forces OR van der
Waals’ forces than Cl2
OR
S8 has more electrons 9
Explain the decrease in the atomic radii across the period from Na to Cl.
nuclear charge increases/ protons increase 9
electrons added to the same shell
OR
screening OR shielding remains the same 9
greater attraction OR greater pull 9
) Describe and explain the trend, down the group, in the reactivity of the Group 2 elements with water.
reactivity increases (down the group) 9 atomic radii increase OR there are more shells 9 there is more shielding OR more screening 9 the nuclear attraction decreases OR Increased shielding and distance outweigh the increased nuclear charge 9 easier to remove (outer) electrons OR ionisation energy decreases 9
suggest why volume of hydrogen would be less when than using pure barium
Less barium to react OR
some barium has already reacted 9
