Which of the following can be classified as a mixture and not as a pure substance?
I. oxygen
II. antifreeze
III. distilled water
IV. human blood
V. brass alloy
A) II and V
B) II and III
C) I only
D) II, IV, and V
The correct answer and explanation is :
The correct answer is A) II and V.
Here’s a detailed explanation:
Mixtures are substances composed of two or more different elements or compounds that are physically combined, not chemically bonded. The components of a mixture can be separated by physical methods (such as filtration, distillation, or evaporation). A pure substance, on the other hand, consists of a single type of element or compound with a fixed composition and can’t be physically separated into other substances.
Now, let’s evaluate each item:
- Oxygen (I):
- Oxygen is a pure substance. It is a chemical element (O), and its composition does not vary. It cannot be separated into simpler substances by physical means, making it a pure substance rather than a mixture.
- Antifreeze (II):
- Antifreeze is a mixture. Typically, it consists of a mixture of water and chemicals like ethylene glycol or propylene glycol. These substances are mixed together physically but not chemically bonded, meaning antifreeze is a mixture, not a pure substance.
- Distilled Water (III):
- Distilled water is a pure substance. It is water that has been purified by distillation, removing impurities and other dissolved substances. The composition is essentially H2O, and it is a pure substance, not a mixture.
- Human Blood (IV):
- Human blood is a mixture. It consists of various components such as plasma, red blood cells, white blood cells, and platelets, which are physically mixed but not chemically bonded. These components can be separated by physical methods like centrifugation, which makes blood a mixture, not a pure substance.
- Brass Alloy (V):
- Brass is a mixture (specifically, an alloy), typically composed of copper and zinc. Alloys are mixtures of metals or a metal and non-metal that are combined physically. Since the elements in brass retain their individual properties and can be separated by physical means, it is a mixture.
Conclusion:
- Oxygen (I) and distilled water (III) are pure substances.
- Antifreeze (II), human blood (IV), and brass alloy (V) are mixtures.
Therefore, the correct answer is A) II and V, as these are the mixtures.