Answer:
7.1
Explanation:
equation to calculate pH is

Answer:
D.
Explanation:
The reaction is losing potential energy, which means that the reaction is losing that energy as heat. Exothermic is the loss of energy. Therefore it will be D.
Answer:
only chlorine can expand its octet.
Explanation:
An atom can expand its octet is it has empty d orbital
the electronic configuration of given elements will be:
B : 1s2 2s2 2p1 [Valence shell n =2 no d orbital]
O :1s2 2s2 2p4 [Valence shell n =2 no d orbital]
F : 1s2 2s2 2p5 [Valence shell n =2 no d orbital]
Cl :1s2 2s2 2p6 3s2 3p5 3d0 [Valence shell n =2 no d orbital]
Out of given elements only chlorine has empty d orbitals in its valence shell
Thus only chlorine can expand its octet.