1. In a science Quiz Competition, Dhani are asked a question where she had to choose the statement which was/ were incoorect?
a. Fractional distillation is the process of separating two or more miscible liquid liquids by distillation.
b . A mixture of immiscible liquids is separated by using an apparatus called separating funnel.
c. A mixture of alcohol and water can be separated by fractional distillation.
d. Crystallization is not better technique than evaporation of dryness.
Answers
Answer:
Correct option is
B
Fractional distillation is a method used for separating homogeneous mixture of two liquids.
C
All pure substances are homogeneous in nature.
D
The constituent elements of a compound can be separated only by chemical reactions.
When we try to mix oil and water, the oil floats to the top since it is less dense than water. So oil is immiscible in water.
Homogeneous liquid mixtures are separated using fractional distillation.
A homogeneous mixture has a uniform composition. Similarly, a pure substance is also made up of only one kind of atom or molecule and has a uniform composition. Hence pure substances are homogeneous in nature.
When two or more elements are chemically bonded together, a compound is formed. Compounds once formed, cannot be separated by physical methods and require chemical treatment for separation. Thus except for option A, all the other options are correct.
a. Fractional distillation is the process of separating two (or more) miscible liquids by distillation, the distillate being collected in fractions boiling at different temperatures. A mixture of two miscible liquids can be separated by the process of fractional distillation.
b. Two immiscible liquids, such as oil and water, can be separated by using a separating funnel. Later the mixture is placed in a separating funnel or colloquially sep funnel and allowed to stand. The oil and water form two separate layers, with the less dense liquid being on top.
c. For example, liquid ethanol can be separated from a mixture of ethanol and water by fractional distillation. This method works because the liquids in the mixture have different boiling points. When the mixture is heated, one liquid evaporates before the other. Vapour forms in the air above the mixture in the flask.
d. Crystallisation is better than evaporation because during Evaporation. Some solids decompose or some, like sugar, may get charred on heating to dryness. Impure solids are obtained by evaporation and are further purified by crystallisation. e.g. salt obtained from the sea is further purified by this method.
[tex][/tex]