The group VIA elements are called chalcogens because most ores of copper (Greek chalkos) are oxides or sulfides, and such ores contain traces of selenium and tellurium.
Huh what type of question is that?!
Answer:
Two, KCl and PbCl₂.
Explanation:
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In this case, since the addition of chloride ions promote the following three ionic reactions:
We can infer that both silver chloride and lead (II) chloride are precipitated products as their Ksp are 6.56x10⁻⁴ and 1.59x10⁻⁵ respectively, which means they are merely soluble in water.
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Answer : The correct option is, 
Explanation :
Amino acid : The acid that contains two functional groups that are carboxylic group, 
and ammine group, .
When the two or more that two amino acids join together with the help of peptide bond, they produces polypeptide chain or protein.
The bond present between the two amino acid is called a peptide bond.
The peptide bond is a chemical bond that is formed between the two molecules when the nitrogen of one amino acid react with the carbon of another amino acid by releasing a water molecule. This is a dehydration synthesis or condensation reaction.
From this we conclude that, only two functional groups carboxylic group, and ammine group, are present in all amino acids.
Hence, the correct option is,
Answer:
physical change because the gaseous water is chemically the same as the liquid
Explanation:
Matter can be defined as anything that has mass and occupies space. Any physical object that is found on earth is typically composed of matter. Matter are known to be made up of atoms and as a result has the property of existing in states.
Generally, matter exists in three (3) distinct or classical phases and these are; solid, liquid and gas.
A physical change can be defined as a type of change that only affects the physical form of a chemical substance (matter) without having any effect on its chemical properties. Thus, a physical change would only affect the physical appearance and properties of a chemical substance (matter) but not its chemical properties.
This ultimately implies that, a physical change result in a change of matter from one form or phase (liquid, solid or gas) to another without a corresponding change in chemical composition.
Hence, the boiling of water is considered to be a physical change because the gaseous water is chemically the same as the liquid i.e there isn't any changes in chemical composition of water when boiling.
