In most cases, when two elements form a compound, the new compound has a set of chemical properties that are entirely different from its reactants. However, in the case of diatomic compounds, such as O2, then yes, the compound retains the properties of its elemental parts.
Answer:
The mass number (A), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. The mass number is different for each different isotope of a chemical element.
The nucleus of a atom contains the protons and the neutrons all most all of the atoms mass is weigh by the protons and the neurons.
According to law of conservation of mass.
In a chemical reaction Mass is neither created nor destroyed.
- Mass of product =Mass of reactant
#1
Mass of water

#2
Mass of sulphur:-

X=240 g NaCl salt dissolves in solution.
Example: If we add 68 g sugar and 272 g water to 160 g solution having concentration 20 %, find final concentration of this solution.
Solution:
Mass of solution is 160 g before addition sugar and water.
100 g solution includes 20 g sugar
160 g solution includes X g sugar
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X=32 g sugar
Mass of solute after addition=32 + 68=100 g sugar
Mass of solution after addition=272 +68 + 160=500 g
500 g solution includes 100 g sugar
100 g solution includes X g sugar
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X= 20 % is concentration of final solution.