Final answer:
From the given list, Helium (a) and Carbon (b) are pure elements. Water, KCl, salt water, air, blood, and cereal with milk are either compounds or mixtures and not pure elements. So, the correct option is A and B.
Step-by-step explanation:
The question at hand is asking us to identify pure elements from a given list. A pure element is a substance that consists of only one type of atom, distinguishing it from a compound or a mixture. Below is the analysis of the given list is-
- a - Helium (He): Helium is a noble gas and is indeed a pure element.
- b - Carbon (C): Carbon is a non-metal and is also a pure element.
- c - Just Water (H2O): This is not a pure element; it is a compound made of hydrogen and oxygen.
- d - KCl (potassium chloride): This is not a pure element; it is a compound made of potassium and chlorine.
- e - Salt Water: This is a mixture of water (H2O) and sodium chloride (NaCl), so it is not a pure element.
- f - Air: Air is a mixture of various gases, mainly nitrogen and oxygen, and is not a pure element.
- g - Blood: Blood is a complex mixture of cells, proteins, and other substances, not a pure element.
- h - Cereal and Milk: This is a mixture of various substances and is certainly not a pure element.
Based on the options provided, the pure elements listed are Helium (a) and Carbon (b).