Which statement describes both homogeneous mixtures and heterogeneous mixtures?
a. their components can distinguish visually
b. their components are combined in a fixed ratio
c. their components can be separated by a physical process
d. they always contain a liquid component
e. they are considered to be pure substances

C

Explanation:

Mixtures can be separated physically, while compounds cannot.

For example if we have mixture of water and alcohol ethanol, we can separate water and ethanol with distillation (process of heating and cooling). Ethanol and water have different boiling points (physical property).

But if we want to separate water (compound) into oxygen and hydrogen, we must break bonds between oxygen and hydrogen and that is not physical property.

c. because step up transformer steps up the input voltage i.e increases the input voltage  

the number of turns are greater on the secondary side of step up transformer  

transformer does not handle dc current

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.