Answer:
d. why matter exists
Explanation:
The kind of questions that chemistry CANNOT answer is "why matter exists".
In Chemistry, question of how the properties, composition and structure of substances are is answered. Also, the transformations that these substances undergo, and the energy that they release or absorbe during the transformation processes are revealed in chemistry.
Chemistry can answer the question of what forms of matter exists but cannot answer why matter actually exists.
Answer : Yes, a precipitate form when a solution of calcium chloride and a solution of mercury(I) nitrate are mixed together.
The net ionic equation will be,
Explanation :
In the net ionic equations, we are not include the spectator ions in the equations.
Spectator ions : The ions present on reactant and product side which do not participate in a reactions. The same ions present on both the sides.
The given balanced ionic equation will be,
The ionic equation in separated aqueous solution will be,
In this equation, 
are the spectator ions.
By removing the spectator ions from the balanced ionic equation, we get the net ionic equation.
The net ionic equation will be,
Answer:
Explanation: By adding base to a solution increases concentration of OH ions.
<span>The lungs are the main organ of the respiratory system, which carries oxygen through the body by means of red blood cells and picks up carbon dioxide, a waste gas, to expel from the body when an organism exhales. The trachea filters the inhaled air and branches into the bronchi, where the air tubes carry air directly into the lungs. The diaphragm is the main muscle of the respiratory system, contracting to increase the volume of the lungs and carry air into the body and expanding to force air out of the lungs.</span>
