Acid-base neutralization reaction is defined as reaction of acid with base to form corresponding salt and water. Strong acid and base completely neutralize each other.
(a) The acid base neutralization reaction is as follows:

From the above balanced chemical reaction, 1 mol of NaOH completely reacts with 1 mol of HCl. The mass of NaOH is given 4.85 g, convert this into number of moles as follows:

Molar mass of NaOH is 39.997 g/mol, thus,

Thus, 0.121 mol of NaOH reacts with same amount of HCl and number of moles of HCl will be 0.121 mol.
Since. molar mass of HCl is 36.46 g/mol, thus, mass can be calculated as follows:

Therefore, 4.421 g of HCl completely reacts with 4.85 g of NaCl.
(b) The acid base neutralization reaction is as follows:

From the above balanced chemical reaction, 1 mol of
completely reacts with 2 mol of
. The mass of
is given 4.85 g, convert this into number of moles as follows:

Molar mass of
is 74.093 g/mol, thus,

Thus, 0.06545 mol of
reacts with
of 
Since. molar mass of
is 63.01 g/mol, thus, mass can be calculated as follows:

Therefore, 8.25 g of
completely reacts with 4.85 g of
.
(c) The acid base neutralization reaction is as follows:

From the above balanced chemical reaction, 2 mol of KOH completely reacts with 1 mol of
. The mass of KOH is given 4.85 g, convert this into number of moles as follows:

Molar mass of KOH is 56.1056 g/mol, thus,

Thus, 0.0864 mol of KOH reacts with
of 
Since. molar mass of
is 98.079 g/mol, thus, mass can be calculated as follows:

Therefore, 4.24 g of KOH completely reacts with 4.85 g of
.