Assertion: All homogenous substances are pure.
Reason: Alloys are homogeneous mixtures of solids.
A. Both assertion and reason are correct and reason is the correct explanation for assertion.
B. Both assertion and reason are correct but reason is not the correct explanation for assertion.
C. Assertion is correct but reason is incorrect
D. Assertion is incorrect but reason is correct

Hint: As we know that the term ‘homo’ means the same, so homogenous mixtures are those in which components that are mixed are equally distributed throughout the mixture. These are also called solutions.

Complete answer:
- It is found that alloys are homogeneous mixtures of two or more than two metals. But as alloy is considered as homogenous, it doesn’t mean that it should be pure.
- As we know that homogenous term indicates that the substance has the same composition throughout. But, on the other hand, pure substances are those substances that cannot be separated by physical process, without breaking its chemical chain. It is found that homogenous mixtures can be separated easily by using various physical methods.

- Hence, we can conclude that the correct option is (d), that is Assertion is incorrect but reason is correct.

Note: - We should note the difference in between homogeneous and heterogeneous mixtures. A homogeneous mixture is those that has uniform composition, has only one phase and can’t be separated physically.
- Whereas, heterogeneous mixtures are those that don't have uniform composition, have two or more phases and can be separated out physically.