Question

Calcium reacts with water according to the chemical equation below: Ca + 2H20 --> Ca(OH)2 + H2 All but which reaction is expected to occur on the basis of the reaction of calcium and water? A. Ra + 2H20 --> Ra(OH)2 + H2 OB. Sr+ 2H20 --> SH(OH)2 + H2 OC. Al + 2H20 > A(OH)2 + H2 OD. Mg + 2H20 --> Mg(OH)2 + H2 O E. Be + 2H2O -> Be(OH)2 + H2

Answer 1

Elements in the same group have similar chemical properties.

Ca is in group 2 of the periodic table. Other elements belonging to group 2 of the periodic table will display similar chemical properties, i.e. will display the same reaction with water.

Be, Mg, Sr, and Ra belong to group 2 of the periodic table and will show a similar reaction with water. Thus options A, B, D, E are reactions that are expected to occur.

Option C is the correct answer:

• Aluminium is in group 13 of the periodic table. It is not in the same group as Ca so the reaction between Al and water will not be the same as Ca.
• Aluminium has 3 valence electrons in its outermost shell. Thus it tends to form the Al3+ cation.
• So, its hydroxide will be Al(OH)3 as opposed to Al(OH)2 which is mentioned in option B.