When vinegar and baking soda react together what new substance is produced?
Carbon dioxide, water and sodium acetate.
The active material in vinegar is acetic acid which is present at somewhere between 5 and 20% w/w depending on the grade (the product you can buy in shops is closer to 5%). Baking soda is sodium hydrogen carbonate or "sodium bicarbonate". The reaction proceeds as follows:
The reaction yields carbon dioxide gas, water, and sodium acetate, which is the sodium salt of acetic acid. This is formed in aqueous solution.