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