Answer:
(a) (i) All the elements of a group have similar chemical properties because they have same no. of valence electrons in their outermost shell. (ii) All the elements of a period have different chemical properties because they have different no. of valence electrons in their atoms.
A buffer is a solution that can resist pH change upon the addition of an acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable. This is important for processes and/or reactions which require specific and stable pH ranges. Buffer solutions have a working pH range and capacity which dictate how much acid/base can be neutralized before pH changes, and the amount by which it will change.
To minimize the sharp pH shift that occurs when a strong acid is added to a solution, IT IS PRACTICAL TO ADD A WEAK BASE.
When a strong acid is added to a solution, it usually brings about a sharp change in the pH of the concerned solution. To avoid this, one can add a weak base to the solution first. The weak base will serves as a buffer for the strong acid and prevents the solution from experiencing sharp pH variations.
