Redox, Group 2 and Group 7 hw ms - REDOX GROUP 2 AND GROUP...

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REDOX, GROUP 2 AND GROUP 7 HW MARK SCHEME 1. (a) RaC l 2 1 (b) Reduction is gain of electrons/decrease in oxidation number Ra 2+ gains 2 electrons Ra/ Oxidation state goes from 2 in RaC l 2 0 in Ra 2 [3] 2. (i) Mg oxidation number changes from 0 to (+)2 OR oxidation number increases by 2 ALLOW correct oxidation numbers shown in equation 2nd mark is dependent on identification of Mg IGNORE electrons 2 (ii) Mg/solid dissolves OR Mg/solid disappears OR (Mg/solid) forms a solution bubbles OR fizzes OR effervesces OR gas produced IGNORE metal reacts IGNORE temperature change IGNORE steam produced DO NOT ALLOW carbon dioxide gas produced DO NOT ALLOW hydrogen produced without gas 2 [4] 3. (i) because Ca has changed from 0 to +2 (1) and H has changed from +1 to 0 (1) 2 (ii) Calcium reacts with water producing hydrogen/H 2 /calcium/hydroxide/Ca(OH) 2 (1) (i.e. one product) Ca(s) + H 2 O(l) Ca(OH) 2 (aq) + H 2 (g) (1) (i.e. full equation) Equation would subsume both two marks 2 [4] 4. Oxidation state goes from 0 in O 2 2 in MgO [2] 5. (i) loss (of electrons) 1 (ii) Ba 0 ( )2 (accept 2 ) 2 [3] Paddington Academy 1
Paddington Academy 2
6. (i) 2Mg + O 2 → 2MgO ALLOW multiples. Correct species must be seen IGNORE state symbols 1 (ii) Fizzes OR bubbles OR gas produced OR effervescing DO NOT ALLOW ‘carbon dioxide gas produced’ DO NOT ALLOW ‘hydrogen produced’ without ‘gas’ Mg dissolves OR Mg disappears OR a solution is formed ALLOW ‘it for Mg’ IGNORE Mg reacts IGNORE temperature change IGNORE steam produced 2 (iii) Quicker OR more vigorous OR gets hotter MUST be a comparison of a reaction observation, not just ‘more reactive’ ALLOW any comparison of greater rate including more bubbles etc. DO NOT ALLOW more gas produced 1 [4] 7. (i) effervescence/bubbles Ra disappears/dissolves 2 (ii) 8-14 1 [3] 8. (a) BaO Ba 3 N 2 Treat any shown charges as working and ignore. Treat B for Ba as a slip 2 (b) any pH > 7 but <15 ALLOW a correct range of pH. 1 (c) Less barium to react OR some barium has already reacted ALLOW less volume because contains some BaO or Ba 3 N 2 1 Paddington Academy 3
(d) reactivity increases (down the group) atomic radii increase OR there are more shells there is more shielding OR more screening the nuclear attraction decreases OR Increased shielding and distance outweigh the increased nuclear charge easier to remove (outer) electrons OR

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