Question

At 21.5 degrees Celsius, a 20mL aliquot of calcium hydroxide is titrated with 16.40mL of 0.050M hydrochloric acid.

a) Calculate the [OH-] concentration from the titration. The neutralisation reaction is Ca(OH)2 + 2HCl ---> CaCl2 + 2H2O

b) Calculate the [Ca^2+] concentration.

c) Calculate the Ksp for calcium hydroxide.

d) Explain when and why the use of a centrifuge might improve the result.

e) Compare the accepted value of Ksp for calcium hydroxide to this experiments value and discuss reasons for discrepancy.

f) Likely reasons for titres to increase with each trial.

g) Is it possible to predict the dissolution of calcium hydroxide as endothermic or exothermic?

Answer 1

Answer (a) Vha - 16. une Sice - 0.05(M) each), = 20 me Sca(OH)₂ = ? v=volume S=Strength From the formula callows x Scallow) = Vie x Suice (M) Scoot) = 2016. uxo.5 20 0.041(M) Therefore, Strength of Calon),(s) Ca(OH)₂ = 0.041 (M) [Ca ²+ ] + 2006 Jan Hence conc of Low-J - 2xo.oul - 0.082 (M) (6) Conc of [Ca 2+] = x 0.041 = 0.041 (e) kep = [ca24] [ 2014-72 = (0.041)*(0,082)² 0.000275684 2.76 x 10-4 ~ (2) et hindered, this can be when the pgroduct (salt) formed during tithation is insoluble, it might create error in the result as complete titnation may get hindered, thie avoided by the use of centrifuge, which helps Separation of insoluble solid particles & facilate & ticles & facilate the titration