Answer:
a.monadioxide
Explanation:
for maintaince of different gases in the air to separate reactions of chemicals
Answer:
A) 
Explanation:
m = Mass of water = 38.9
M = Molar mass of water = 18 g/mol
= Avogadro's number = 
The reaction of electrolysis would be
Number of moles of 
From the reaction it can be seen that 2 moles of gives 1 mole of 
So, number of moles of produced is
Number of molecules
So, of oxygen is produced.
Answer:
A change is called irreversible if it cannot be changed back again. In an irreversible change, new materials are always formed.
Explanation:
<u>Answer:</u>
<em>Silver tarnishing as the silver metal reacts with sulphur is a chemical change.</em>
<u>Explanation:</u>
Tarnishing is the process of chemical change occurring on the surface of objects leading to corrosion or other defects on the surface. The remaining options like dilution, eroding is a physical change where the concentration of salt and rock particles will be decreased, respectively.
Similarly for soil drying also the concentration of water will be decreased leading to a physical change from wetty or dry soil.
But the last option which indicates tarnishing of silver metal on reaction with sulphur is a chemical process as the surface of silver metal will be reacting to sulphur and leads to lose of electrons which leads to corrosion of the surface or tarnishing of silver.
