Question

what volume of 5.00*10^-3 M HNO3 is needed to titrate 50.00 mL of 5.00*10^-3 M Ca(OH)2 to the equivalence point?

Answer 1

Balanced equation:
Ca(OH)₂ + 2 HNO₃ ====> Ca(NO₃)₂ + 2 H₂O

One equivalent of Ca(OH)₂ needs 2 equivalent of HNO3. In given problem the concentration of HNO3 and Ca(OH)2 is same. Hence we can double the volume of HNO3

Ca(OH)2 =   50.00 mL of 5.00 x 10^-3

HNO₃ = 100 ml of 5.00 x 10^-3

Hence we need 100 ml volume of 5.00 x 10^-3 M HNO3

Since Ca(OH)2 needs 2 equivalent of HNO3 we can write the formula as below

V1 x N1 = 2 V2 x N2

V1 = ?

N1 = 5.00 x 10^-3 M

V2 = 50 ml

N2 = 5.00 x 10^-3 M

substitute in the equation and find V1

V1 = 2 x 50 x 5.00 x 10^-3 / 5.00 x 10^-3 = 100 ml

Hence 100 ml of 5.00 x 10^-3 M HNO3 is need