Answer:
According to Bohr, the amount of energy needed to move an electron from one zone to another is a fixed, finite amount. ... The electron with its extra packet of energy becomes excited, and promptly moves out of its lower energy level and takes up a position in a higher energy level. This situation is unstable, however.
Pressure has little effect on the solubility of liquids and solids because they are almost incompressible True.
Liquids and solids show little change in solubility with changes in pressure. As expected, gases increase in solubility with increasing pressure. Henry's Law states that the solubility of a gas in a liquid is directly proportional to the pressure of that gas above the surface of the solution.
External pressure has little effect on liquid and solid solubility. In contrast, the solubility of a gas increases as the partial pressure of the gas above the solution increases.
Solubility is a measure of the concentration of dissolved gas particles in a liquid and is a function of gas pressure. Increasing the gas pressure increases the number of collisions and increases the solubility, and decreasing the pressure decreases the solubility.
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Answer: The ion that contribute to water hardness are:
--> a. Ca2+
--> b. (HCO)3^- and
--> c. Mg2+
While K+ DOES NOT contribute to water hardness.
Explanation:
WATER in chemistry is known as a universal solvent. This is so because it is polar in nature and dissolves most inorganic solutes and some polar organic solutes to form aqueous solutions. It is composed of elements such as hydrogen and oxygen in the combined ratio of 2:1.
Water is said to be HARD if it does not lather readily with soap. There are two types of water hardness:
--> Permanent hardness: This is mainly due to the presence of CALCIUM and MAGNESIUM ions in the form of soluble tetraoxosulphate(VI) and chlorides. These ions are removed by adding washing soda or caustic soda.
--> Temporary hardness: This is due to the presence of calcium HYDROGENTRIOXOCARBONATES. It can be removed by boiling and using slaked lime.
Therefore from the above given ions, Ca2+,(HCO)3^- and Mg2+ contributes to water hardness.
Answer: 0.8541 grams of HCl will be required.
Explanation: Moles can be calculated by using the formula:
Given mass of 
= 0.610 g
Molar mass of = 78 g/mol
Number of moles of = 0.0078 moles
The reaction between and HCl is a type of neutralization reaction because here acid and base are reacting to form an salt and also releases water.
Chemical equation for the above reaction follows:
By Stoichiometry,
1 mole of reacts with 3 moles of HCl
So, 0.0078 moles of will react with 
= 0.0234 moles
Mass of HCl is calculated by using the mole formula, we get
Molar mass of HCl = 36.5 g/mol
Putting values in the equation, we get
Mass of HCl required will be = 0.8541 grams
Semi-conductor,brittle not malleable or ductile.
