Indicative points:
- IP1: Ca((s))+2H2O((l))→Ca(OH)2((aq))+H2(( g))
- IP2: effervescence
- IP3: (indicator) turns blue
- IP4:
faster / more vigourous reaction with calcium and
linked to an observation
OR
no (observable) reaction with magnesium
- IP5:
Ca has lower ionisation energy
OR
Ca has more shielding / more shells / larger atoms
- IP6:
darker blue / more alkaline / higher pH with Ca and
linked to greater solubility of Ca(OH)2
Ignore any reference to C a / M g dissolving
Allow multiples
Ignore state symbols
Ignore equations involving magnesium
Allow fizzing/bubbling
Allow turns purple
If stated, initial colour must be green/yellow Ignore forms solution with pH>7
Accept reverse arguments
eg reaction with calcium:
- has faster bubbling
- changes colour faster
- forms (white) ppt faster
- gets hotter (Ignore more exothermic)
- (solid) disappears faster
Ignore (indicator) remains green with Mg Ignore no (white) ppt with Mg
Accept reverse arguments
Allow Ca has less attraction on (outer) e(−)
Allow Ca loses electron(s) more easily Ignore calcium ions/ Ca2+ for calcium/Ca
Accept reverse arguments
Ignore less (white) ppt with Ca
Allow hydroxide solubility increases down group Allow Mg(OH)2 insoluble
Ignore explanations of solubility