A 11.38 g sample of a weak acid (HA) is dissolved in 535.0 g of water. The freezing point of the solution is −0.368 °C . The molar mass of the weak acid is 93.0 g/mol. Calculate the acid dissociation constant, a , of the weak acid.

Ido not understand. 

Ibelieve it's temperature! i'm not 100% sure.

Reaction involved in present system is :   c12h22o11 + h2o → 2 c6h12o6the reaction system is obeying following rate law:   rate = k[c12h22o11]thus, it is a first order reaction.now, for 1st order reactionrate constant (k) =  given: initial conc. = 3.0 g, final conc. = 2.7 g, t = 2.5 h∴rate constant (k) =  ∴ k = 0.04215 h-1now, for 1st order reaction, half life = 0.693/k = 0.693/0.04215 = 16.4 hthus correct answer is option b

Aand x are the answers to your question.hope it !