This is an acid-base reaction (neutralization): HNO3 is an acid, Na2CO3 is a base.
This is a gas evolution reaction, CO2 is the formed gas.
Reactants:
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HNO3 – Nitric acid
Other names: Aqua fortis, Spirit of niter, Eau forte
Appearance: Colorless, yellow or red fuming liquid ; Colourless-to-yellow liquid with pungent odour ; Colorless, yellow, or red, fuming liquid with an acrid, suffocating odor. [Note: Often used in an aqueous solution. Fuming nitric acid is concentrated nitric acid that contains dissolved nitrogen dioxide.]
Na2CO3 – Sodium carbonate
Other names: Soda ash, Washing soda, Soda crystals
Appearance: White solid, hygroscopic ; White hygroscopic powder
Products:
NaNO3 – Sodium nitrate
Other names: Peru saltpeter, Soda niter, Cubic niter
Appearance: White powder or colorless crystals ; Colourless hygroscopic crystals
CO2
Names: Carbon dioxide, {{plainlist|, CO2
Appearance: Colorless gas ; Odourless colourless compressed liquefied gas ; Colorless, odorless gas. [Note: Shipped as a liquefied compressed gas. Solid form is utilized as dry ice.]
H2O – Water, oxidane
Other names: Water (H2O), Hydrogen hydroxide (HH or HOH), Hydrogen oxide
Appearance: White crystalline solid, almost colorless liquid with a hint of blue, colorless gas