Answer
Avogadro's number: One mole of any substance contains 6.022×10²³ molecules
Explanation
While finding the number of moles of oxygen molecules present in 3.65 moles of Na2SO4 the conversion factor used would be Avodagro's number, which is
One mole of any substance contains 6.022×10²³ molecules.
When sodium carbonate is dissolved in water, the equation is
.
When carbon dioxide is placed in water, aqueous carbon dioxide is formed: 
<h3>Dissolution of compounds in water</h3>
Some compounds are water-soluble, some are just partially soluble, while others are insoluble in water. Some soluble or partially soluble substances dissociate in water into their component ions. These substances are said to be ionic.
Sodium carbonate, like every other sodium salt, is soluble in water. It dissolves in water to form an aqueous solution of sodium carbonate.
While in solution, sodium carbonate dissociates into its component ions according to the following equation:

Carbon dioxide, on the other hand, does not dissociate in water. Instead, it dissolves in water where most of it remains as aqueous carbon dioxide in equilibrium with a small amount of hydronium ion and hydrogen carbonate ion.
Since the hydronium and hydrogen carbonate ions formed are so minute, the equation of the reaction can be written as: 
More on the dissolution of substances can be found here: brainly.com/question/28580758
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If in the solution, half of the added solute fails to dissolve. The solution started out supersaturated. The correct option is b.
<h3>What is supersaturation?</h3>
Supersaturation is the condition where the solutes exceed the amount that can be dissolved in a solution.
Supersaturation occurs when the solute no longer mix in the solution.
Thus, the correct option is b. The solution started out supersaturated.
Learn more about supersaturation
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1 molecule of glucose contains 6 atoms of C, 12 atoms of H , and 6 atoms of 0.1 mole of glucose contains 6 moles of C atoms , 12 moles of H atoms , and 6 moles of O atoms .