If it takes 25 mL of 1.1 M Ca(OH)2 to neutralize 55 mL of an HNO3 solution, what is the concentration of the HNO3?

1M

Explanation:

Given parameters:

Volume of Ca(OH)₂  = 25mL   = 0.025dm³

Concentration  = 1.1M

Volume of HNO₃  = 55mL  = 0.055dm³

Unknown:

Concentration of HNO₃ = ?

Solution:

To solve this problem, we must bear in mind that this an acid-base titration. In this reaction, an acid is used to neutralize a base.

 The reaction equation is shown below;

            Ca(OH)₂    +   2HNO₃    →   Ca(NO₃)₂   +   2H₂O

Start from the given and known reactant first. Here it is Ca(OH)₂ ;

  Find the number of moles of  Ca(OH)₂ first.

   Number of moles  Ca(OH)₂   = concentration x volume

                                    = 1.1    x   25 x 10⁻³

                                     = 0.028moles

From  the reaction equation;

                   1 mole of Ca(OH)₂  reacted with 2 moles of HNO₃

                  0.028 moles of Ca(OH)₂ will react with 2 x 0.028

                                                 = 0.055moles of HNO₃

Now that we know the number of moles, we can find the concentration of HNO₃;

              Concentration of HNO₃ =

                                                         =

                                                         = 1M