化學mc question(15 marks)

第一條答案係 A
雖然Sulphur Dioxide本身是中性，但當溶落水就變成Sulphurous Acid( H2SO3 )
Chemical reaction : SO2 + H2O => H2SO3 => Acid in (aq) state

第二條答案係 A(但解釋同上面既樓主有少少唔同)
首先，能夠與dilute sulphuric acid有反應的只有A和B
Chemical reaction of A :
MgCO3 + H2SO4 => Mg(2+) + CO2 + H2O + SO4(2-)
Chemical reaction of B :
(NH4)2-(CO3) + H2SO4 => 2 NH4(+) + H2O + CO2 + SO4(2-)
由於以上A同B都可以釋出colourless gas( carbon dioxide )，所以只有A與B暫時對‧
跟手， Lead(II) nitrate只可以與A react(因為Mg比Pb活躍，但ammounium比Pb不活躍)
Chemical reaction of A with lead(II) nitrate :，所以做唔到displacement => no precipatation reaction occurs
Chemical reaction of A with lead(II) nitrate :
MgSO4 + PbNO3 => MgNO3 + PbSO4
當中MgNO3是溶得落水的........呢個就係同上面樓主有唔同既地方，white ppt.應該是PbSO4( Lead(II) sulphate )才對‧

1.A
To neutralize an alkaline solution, acidic substance is used. Only A is acidic.

4.A
colourless gas is carbon dioxide. So the anion is carbonate. Magnesium nitrate formed is insoluble in water so white ppt appears.

1. b
2. ?