Inorganic ExamQs Flashcards
Use the Periodic Table to deduce the full electron configuration of calcium. (1 mark)
1s2 2s2 2p6 3s2 3p6 4s2
Allow correct numbers that are not superscripted
Write an ionic equation, with state symbols, to show the reaction of calcium with an excess of water. (1 mark)
Ca(s)+ 2H2O(l) –> Ca2+(aq) + 2OH–(aq) + H2(g)
State symbols essential
State the role of water in the reaction with calcium. (1 mark)
oxidising agent
Write an equation to show the process that occurs when the first ionisation energy of calcium is measured. (1 mark)
Ca(g) –> Ca+(g) + e–
State symbols essential
Allow ‘e’ without the negative sign
State and explain the trend in the first ionisation energies of the elements in Group 2 from magnesium to barium. (3 mark)
Decrease
If answer to ‘trend’ is not ‘decrease’, then chemical error = 0 / 3
Ions get bigger / more (energy) shells
Allow atoms instead of ions
Weaker attraction of ion to lost electron
Explain why different observations are made when aqueous barium chloride is added separately to aqueous magnesium sulfate and to aqueous magnesium nitrate.
Write the simplest ionic equation, including state symbols, for any reaction that occurs.
BaSO4 is insoluble but Ba(NO3)2 is soluble
OR
BaSO4 precipitates but Ba(NO3)2 product(s) of second reaction is soluble/remains in solution
OR
BaSO4 is insoluble but no reaction occurs in second case
NOT just ‘no observation’ in second case
Comparison of solubilities must be implied NOT Barium is soluble/insoluble
Ba2+(aq) + SO42-(aq) → BaSO4(s)
Correct state symbols required
Magnesium reacts readily with steam. State two observations you would make when magnesium reacts with steam. Write an equation for the reaction.
White solid / white ash
ALLOW ‘white smoke/powder’
IGNORE ‘product’ NOT ppt
IGNORE fumes
IGNORE tube/glass goes black
Bright light / white light
ALLOW glow/flame for light
Mg + H2O → MgO + H2
IGNORE state symbols
Explain why the first ionisation energy of barium is less than the first ionisation energy of calcium. (2 marks)
More (electron) shells / (outer) electrons further from the nucleus / larger atoms / more shielding
If ‘molecules’ mentioned CE = 0
It = Ba
Mark independently
ALLOW energy levels for shells
Both ideas must be comparative
So weaker attraction of nucleus/protons for (outer) electrons
NOT hold/pull/bonded for ‘attraction’
Idea of nucleus or protons must be clear
ALLOW M2 if electrons implied from mention in M1
ALLOW converse if it is clear that answer refers to Ca
The Group 2 elements react with water.
State the trend in reactivity with water of the elements down Group 2 from Mg to Ba
Write an equation for the reaction of strontium with water.
Increases / gets more reactive / reacts more vigorously / violently (down the Group)
Sr+2H2O—>Sr(OH)2+H2
Credit multiples and correct ionic equations
Ignore state symbols
State the trend in atomic radius for atoms of the elements down Group 2 from Mg to Ba Give a reason for this trend. (2 marks)
M1 Increases / gets bigger
If M1 is incorrect CE = 0 for the clip
If M1 is blank, mark on and seek to credit the correct information in the text
M2 requires a correct M1
M2 More shells or sub-shells or (main) levels or sub-levels or orbitals (of electrons)
If “molecules” penalise M2
Not simply “more electrons”
Not “more outer shells”
Ignore reference to nuclear charge and shielding
Give the formula of the hydroxide of the element in Group 2 from Mg to Ba that is most soluble in water.
Ba(OH)2
This MUST be a formula so ignore the name
Credit Ba2+ 2OH−
Ignore state symbols
From Mg(OH)2 to Ba(OH)2, the solubility in water
increases
From Mg to Ba, the first ionisation energy
decreases
From Mg to Ba, the atomic radius
increases
Explain why calcium has a higher melting point than strontium.
Correct reference to size of cations/proximity of electrons
M1 (For Ca) delocalised electron(s) closer to
cations / positive ions / nucleus
OR cations / positive ions / atoms are smaller
OR cation / positive ion / atom or it has fewer (electron) shells / levels
CE = 0 for reference to molecules or intermolecular forces or covalent bonds
Ignore “Van der Waals forces (between atoms)” but penalise if between “molecules
Ignore general Group 2 statements
Answers must be specific
Penalise M1 if Ca or Sr is said to have more or less delocalised electrons
Ignore reference to shielding
Relative strength of metallic bonding
M2 (For Ca) has stronger attraction between the
cations / positive ions / nucleus and the delocalised electron(s)
OR
stronger metallic bonding
(assume argument refers to Ca but accept converse argument for Sr)
