Question

The M solution required for NaOH in 40.50mL from solution containing 2g of NaOH in 500mL for complete neutralization is :
(A) 10 mL decinormal HCl
(B) 20 mL decinormal HCl
(C) 50 mL decinormal HCl
(D) 25 mL decinormal HCl

Answer 1

Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a chemical species, in particular of a solute in a solution, in terms of amount of substance per unit volume of solution.

Complete step by step solution: We know that 1 molar is equal to 10 decimals.
Molecular mass of NaOH = 40 g
molarity of stock solution = $\frac{2}{40\times 500}\times 1000$ $= 0.1 M$
no. of moles of NaOH in 40.50 ml of solution = $0.1\times \frac{40.5}{1000}~$ $= 0.004504$ $moles$
For neutralisation, we have no. of moles of HCl = no. of moles of NaOH
1 decimolar = 0.1 M
So, number of moles of HCl in 10 ml decimolar solution =$\frac{20}{1000}\times 0.1~$ $= 0.002$
number of moles of HCl in 50 ml decimolar solution =$\frac{50}{1000}\times 0.1$ $= 0.005$
Applying conversion, we get, 0.005 will be equal to 50 mL decinormal.

Hence the correct option is the C option.

Note: A neutralization reaction can be defined as a chemical reaction in which an acid and base quantitatively react together to form salt and water as products. In a neutralization reaction, there is a combination of ${{H}^{+~}}$ ions and $O{{H}^{~}}$ ions which form water. A neutralisation reaction is generally an acid-base neutralization reaction.