有咩酸同咩鹼中和後會產生氣體...要在室溫

不會有的!
中和作用neutralization
的定義是酸(acid)和鹼(alkali)產生化學作用(chemical reaction)後
只會有水(water)及鹽(salt)<---不是氯化鈉(sodium chloride)
word equation係
acid + alkali -----> water + salt
應該沒有salt在室溫情況下是氣體吧
salt係ionic compound所以melting point 會低 d
就係咁la~

以我所知，只有氨化合物(ammonium compound)跟酸中和才會產生氣體，那是氨氣(ammonia)。

Concerning the reaction of an acid with a base which produces carbon dioxide, it is better for you to quote the source for me to have a look.

Regarding "2HCl + Na2CO3 → 2NaCl + H2O + CO2", I heard that some people also regard this reaction as a neutralization. Nonetheless, strictly speaking, it is wrong.