Can we write Sodium Hydrogen Carbonate as Sodium Bicarbonate?

Q. Why is sodium carbonate more soluble than sodium bicarbonate in water. Can we give any general statement that carbonates are more soluble than bicarbonates

Q. Sodium bicarbonate on heating decomposes to form sodium carbonate, ${CO}_2$ and water. If $0.2$ moles of sodium bicarbonate is completely decomposed, how many moles of sodium carbonate is formed?

Q. Sodium bicarbonate on heating decomposes to form sodium carbonate, $C{O}_2$ and water. If $0.2$ mole of sodium bicarbonate is completely decomposed, how many moles of sodium carbonate is formed?

Q. Assertion :Sodium carbonate decompose on heating at a high temperature. Reason: Sodium bicarbonate on heating gives sodium carbonate along with carbon dioxide.

Q. How many grams of calcium carbonate are required to produce enough carbon dioxide which can convert $0.5$ mol of sodium carbonate into sodium bicarbonate?
$CaC{O}_3⟶CaO+C{O}_2$
$N{a}_{2}C{O}_3+H_{2}O+C{O}_2⟶2NaHC{O}_3$