Which of the following are considered pure substances?
2 answers:
Answer: A. Element and B. Compound
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Copper
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: water
Heterogeneous mixture : It is a mixture that has non-uniform composition throughout the solution and the particle size or shapes are also different.There is a physical boundary between the dispersed phase and dispersion medium.
Homogeneous mixture: It is a mixture that has uniform composition throughout the solution and the particle size or shapes are not different.There is no physical boundary between the dispersed phase and dispersion medium.
Thus element and compound are pure substances.
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Answer:
D. all of these
Explanation:
Proteins are chains of amino acids (polypeptides) that adopt a specific conformation in space. To adopt this conformation, the amino acid chains fold locally and regularly, forming what is known as secondary structures. Mainly, there are two types of secondary structures: the α-helix and the β-pleated sheet.
In the α-helix, the polypeptide chain is spirally wound on itself. This structure is maintained thanks to hydrogen bonds between the carboxyl group of an amino acid and the amino group of the fourth amino acid that follows in the chain.
In the β-pleated sheet the polypeptide skeleton is almost extended in a zig zag shape and stability is achieved by the association of two or more peptide chains next to each other by hydrogen bonds between the amino and carboxyl groups of the peptide bond between adjacent chains. For this reason, hydrogen bonds are almost perpendicular to amino acid chains. In the image Bsheet this phenomenon can be observed.
Usually, the chains are drawn with an arrow to indicate the direction of the polypeptide chain from the amino group to the terminal carboxyl. Thus, adjacent chains of a beta sheet can be oriented in the same direction (parallel beta sheets), or in opposite directions (antiparallel beta sheets). The same folded beta sheet can have parallel and antiparallel chains. The image Bsheet 2 shows parallel and antiparallel chains.
CO₂ + 2LiOH ⇒ Li₂CO₃ + H₂O
1mol : 2mol
0,58mol : x