Question

How many milliliters of 0.02 M HCl are needed to react completely with 100 mL of 0.01 M NaOH?

Answer 1

Answer: Option (D) is the correct answer.

Explanation:

Molarity is number of moles divided by volume of the solution.

Mathematically,     Molarity = $\frac{no. of moles}{Volume}$

Also, in the given situation number of moles of both HCl and NaOH are equal. Therefore, volume of HCl will be calculated as follows.

               $M_{HCl}V_{HCl}$ = $M_{NaOH}V_{NaOH}$

               $0.02 M \times V_{HCl}$ = $0.01 M \times 100 mL$

                $V_{HCl}$ = $\frac{0.01 M \times 100mL}{0.02}$

                                              = 50 mL

Thus, we can conclude that volume of HCl is 50 mL.

Answer 2

The reaction of HCl and NaOH is HCl + NaOH = NaCl + H2O. So the mole number of HCl and NaOH is equal. So the volume of HCl =0.01*0.1/0.02=0.05 L =50 ml. So the answer is D).