Dilute hydrochloric acid cannot be concentrated beyond which of the following concentrations by boiling (in $\%$)?

Which of the following statements is true?

$A$ liquid mixture that boils without changing its composition is called:

Why is it not possible to obtain pure ethanol by fractional distillation? What general name is given to binary mixtures which show deviation from Raoult’s law and whose components cannot be separated by fractional distillation? How many types of such mixtures are there?

Given below are two statements:
Statement $(I)$: $1,2,3$-Trihydroxypropane can be separated from water by simple distillation.
Statement $(II)$: An azeotropic mixture cannot be separated by fractional distillation.

Components of a binary mixture of two liquids $A$ and $B$ were being separated by distillation. After some time,the separation of components stopped and the composition of the vapour phase became the same as that of the liquid phase. Both the components started coming in the distillate. Explain why this happened.