One of the most important characteristic of a metal is its density. As density is the mass of any substance per unit volume. If one can measure the mass of the given shiny metal and its volume then the density of the metal can be determined. The density if matches with the density of the real gold then one can determine the metal is gold or not. The other experiments given will not work in any condition as-
1. Gold doesn't react with water.
2. The hardness of any metals are more than the non-metals and it is not at all an unique property of any metal.
3. All the metals usually reacts with acids or bases with more or less extent. thus it cannot identify the metal is gold or not.
4. The magnetic property is an inherent property of metal. There are several metals which shows magnetic property. Thus gold cannot be identified by this way.
The answer is A. The prokaryote...
Ionic bonds are formed when there is complete transfer of valence electrons between two atoms.
Electronegativity tells the trend of an atom to atract electrons.
You should search for the complete set of rules that indicate whether an ionic or covalent bond happens.
There are two relevant rules to state if whether an ionic bond will happen:
- When the difference of electronegativities between the two atoms is greater than 2.0, then the bond is ionic.
- When the difference is between 1.6 and 2.0, the bond is ionic if one of the elements is a metal.
You need to list the electronegativities of the five elements (there are tables with this information)
Element electronegativity
Cu: 1.9
H: 2.2
Cl 3.16
I: 2.66
S: 2.58
Differences:
Cu / S: 2.58 - 1.9 = 0.68
H / S: 2.58 - 2.2 = 0.38
Cl / S: 3.16 - 2.58 =0.58
I / S: 2.66 - 2.58 = 0.08
Those differences are too low to consider that the bond is ionic.
Then the answer is that none of those atoms forms an ionic bond with sulfur.
The answer is (3) pH 3 to pH 1. The pH is related to the concentration of H3O+ with the relationship: pH = -lg c(H+). So when concentration of H3O+ increase, the pH will decrease. And decrease 2 when when increase hundredfold. Because 100=10^2.
Http://www.chem4kids.com/files/elem_pertable.html this should help.
